An authentication bypass vulnerability was present in the GitHub Enterprise Server (GHES) when utilizing SAML single sign-on authentication with the optional encrypted assertions feature. This vulnerability allowed an attacker to forge a SAML response to provision and/or gain access to a user with site administrator privileges. Exploitation of this vulnerability would allow unauthorized access to the instance without requiring prior authentication. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.13.0 and was fixed in versions 3.9.15, 3.10.12, 3.11.10 and 3.12.4. This vulnerability was reported via the GitHub Bug Bounty program.

GitHub Actions Runner is the application that runs a job from a GitHub Actions workflow. The actions runner invokes the docker cli directly in order to run job containers, service containers, or container actions. A bug in the logic for how the environment is encoded into these docker commands was discovered in versions prior to 2.296.2, 2.293.1, 2.289.4, 2.285.2, and 2.283.4 that allows an input to escape the environment variable and modify that docker command invocation directly. Jobs that use container actions, job containers, or service containers alongside untrusted user inputs in environment variables may be vulnerable. The Actions Runner has been patched, both on github.com and hotfixes for GHES and GHAE customers in versions 2.296.2, 2.293.1, 2.289.4, 2.285.2, and 2.283.4. GHES and GHAE customers may want to patch their instance in order to have their runners automatically upgrade to these new runner versions. As a workaround, users may consider removing any container actions, job containers, or service containers from their jobs until they are able to upgrade their runner versions.

Impact

CommonMarker uses cmark-gfm for rendering Github Flavored Markdown. An integer overflow in cmark-gfm's table row parsing may lead to heap memory corruption when parsing tables who's marker rows contain more than UINT16MAX columns. The impact of this heap corruption ranges from Information Leak to Arbitrary Code Execution.

If affected versions of CommonMarker are used for rendering remote user controlled markdown, this vulnerability may lead to Remote Code Execution (RCE).

Patches

This vulnerability has been patched in the following CommonMarker release:

- v0.23.4

Workarounds

The vulnerability exists in the table markdown extensions of cmark-gfm. Disabling any use of the table extension will prevent this vulnerability from being triggered.

References

- https://github.com/github/cmark-gfm/security/advisories/GHSA-mc3g-88wq-6f4x

Acknowledgements

We would like to thank Felix Wilhelm of Google's Project Zero for reporting this vulnerability

For more information

If you have any questions or comments about this advisory:

Open an issue in CommonMarker

An unsafe reflection vulnerability was identified in GitHub Enterprise Server that could lead to reflection injection. This vulnerability could lead to the execution of user-controlled methods and remote code execution. To exploit this bug, an actor would need to be logged into an account on the GHES instance with the organization owner role. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.12 and was fixed in versions 3.8.13, 3.9.8, 3.10.5, and 3.11.3. This vulnerability was reported via the GitHub Bug Bounty program.

An XML signature wrapping vulnerability was present in GitHub Enterprise Server (GHES) when using SAML authentication with specific identity providers utilizing publicly exposed signed federation metadata XML. This vulnerability allowed an attacker with direct network access to GitHub Enterprise Server to forge a SAML response to provision and/or gain access to a user with site administrator privileges. Exploitation of this vulnerability would allow unauthorized access to the instance without requiring prior authentication. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.14 and was fixed in versions 3.13.3, 3.12.8, 3.11.14, and 3.10.16. This vulnerability was reported via the GitHub Bug Bounty program.

Registrator is a GitHub app that automates creation of registration pull requests for julia packages to the General registry. Prior to version 1.9.5, if the clone URL returned by GitHub is malicious (or can be injected using upstream vulnerabilities) a shell script injection can occur within the withpasswd function. Alternatively, an argument injection is possible in the gettreesha function. either of these can then lead to a potential RCE. Users should upgrade immediately to v1.9.5 to receive a fix. All prior versions are vulnerable. No known workarounds are available.

Registrator is a GitHub app that automates creation of registration pull requests for julia packages to the General registry. Prior to version 1.9.5, if the clone URL returned by GitHub is malicious (or can be injected using upstream vulnerabilities), an argument injection is possible in the gettreesha() function. This can then lead to a potential remote code execution. Users should upgrade immediately to v1.9.5 to receive a patch. All prior versions are vulnerable. No known workarounds are available.

An improper access control vulnerability was identified in the GitHub Enterprise Server API that allowed an organization member to escalate permissions and gain access to unauthorized repositories within an organization. This vulnerability affected all versions of GitHub Enterprise Server prior to 2.21 and was fixed in 2.20.9, 2.19.15, and 2.18.20. This vulnerability was reported via the GitHub Bug Bounty program.

An improper access control vulnerability in GitHub Enterprise Server allowed a workflow job to execute in a self-hosted runner group it should not have had access to. This affects customers using self-hosted runner groups for access control. A repository with access to one enterprise runner group could access all of the enterprise runner groups within the organization because of improper authentication checks during the request. This could cause code to be run unintentionally by the incorrect runner group. This vulnerability affected GitHub Enterprise Server versions from 3.0.0 to 3.0.15 and 3.1.0 to 3.1.7 and was fixed in 3.0.16 and 3.1.8 releases.

The Management Console in GitHub Enterprise 2.8.x before 2.8.7 has a deserialization issue that allows unauthenticated remote attackers to execute arbitrary code. This occurs because the enterprise session secret is always the same, and can be found in the product's source code. By sending a crafted cookie signed with this secret, one can call Marshal.load with arbitrary data, which is a problem because the Marshal data format allows Ruby objects.

cmark-gfm is GitHub's extended version of the C reference implementation of CommonMark. Prior to versions 0.29.0.gfm.3 and 0.28.3.gfm.21, an integer overflow in cmark-gfm's table row parsing table.c:rowfromstring may lead to heap memory corruption when parsing tables who's marker rows contain more than UINT16MAX columns. The impact of this heap corruption ranges from Information Leak to Arbitrary Code Execution depending on how and where cmark-gfm is used. If cmark-gfm is used for rendering remote user controlled markdown, this vulnerability may lead to Remote Code Execution (RCE) in applications employing affected versions of the cmark-gfm library. This vulnerability has been patched in the following cmark-gfm versions 0.29.0.gfm.3 and 0.28.3.gfm.21. A workaround is available. The vulnerability exists in the table markdown extensions of cmark-gfm. Disabling the table extension will prevent this vulnerability from being triggered.

An improper limitation of a pathname to a restricted directory vulnerability was identified in GitHub Enterprise Server that enabled remote code execution. A check was added within Pages to ensure the working directory is clean before unpacking new content to prevent an arbitrary file overwrite bug. This vulnerability affected only version 3.7.0 of GitHub Enterprise Server and was fixed in version 3.7.1. This vulnerability was reported via the GitHub Bug Bounty program.

A vulnerability classified as critical was found in purpleparrots 491-Project. This vulnerability affects unknown code of the file update.php of the component Highscore Handler. The manipulation leads to sql injection. The name of the patch is a812a5e4cf72f2a635a716086fe1ee2b8fa0b1ab. It is recommended to apply a patch to fix this issue. The identifier of this vulnerability is VDB-217648.

An incorrect authorization vulnerability was identified in GitHub Enterprise Server, allowing for escalation of privileges in GraphQL API requests from GitHub Apps. This vulnerability allowed an app installed on an organization to gain access to and modify most organization-level resources that are not tied to a repository regardless of granted permissions, such as users and organization-wide projects. Resources associated with repositories were not impacted, such as repository file content, repository-specific projects, issues, or pull requests. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.7.1 and was fixed in versions 3.3.16, 3.4.11, 3.5.8, 3.6.4, 3.7.1. This vulnerability was reported via the GitHub Bug Bounty program.

Summary

A security vulnerability has been identified in GitHub CLI that could allow remote code execution (RCE) when users connect to a malicious Codespace SSH server and use the gh codespace ssh or gh codespace logs commands.

Details

The vulnerability stems from the way GitHub CLI handles SSH connection details when executing commands. When developers connect to remote Codespaces, they typically use a SSH server running within a devcontainer, often provided through the default devcontainer image. GitHub CLI retrieves SSH connection details, such as remote username, which is used in executing ssh commands for gh codespace ssh or gh codespace logs commands.

This exploit occurs when a malicious third-party devcontainer contains a modified SSH server that injects ssh arguments within the SSH connection details. gh codespace ssh and gh codespace logs commands could execute arbitrary code on the user's workstation if the remote username contains something like -oProxyCommand="echo hacked" #. The -oProxyCommand flag causes ssh to execute the provided command while # shell comment causes any other ssh arguments to be ignored.

In 2.62.0, the remote username information is being validated before being used.

Impact

Successful exploitation could lead to arbitrary code execution on the user's workstation, potentially compromising the user's data and system.

Remediation and Mitigation

1. Upgrade gh to 2.62.0 2. Exercise caution when using custom devcontainer images, prefer default or pre-built devcontainers from trusted sources.

An improper neutralization of input vulnerability was identified in GitHub Enterprise Server that allows DOM-based cross-site scripting via Issues search label filter that could lead to privilege escalation and unauthorized workflow triggers. Successful exploitation requires an attacker to have access to the target GitHub Enterprise Server instance and to entice a user, while operating in sudo mode, to click on a crafted malicious link to perform actions that require elevated privileges. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.18.1, 3.17.7, 3.16.10, 3.15.14, 3.14.19.

An improper verification of cryptographic signature vulnerability was identified in GitHub Enterprise Server that allowed SAML SSO authentication to be bypassed resulting in unauthorized provisioning of users and access to the instance. Exploitation required the encrypted assertions feature to be enabled, and the attacker would require direct network access as well as a signed SAML response or metadata document. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.15 and was fixed in versions 3.11.16, 3.12.10, 3.13.5, and 3.14.2. This vulnerability was reported via the GitHub Bug Bounty program.

A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to send crafted requests to internal services by exploiting insufficient input validation in an upload endpoint. By injecting path traversal content into request parameters, an attacker could bypass the intended request flow and redirect internal API calls, potentially accessing internal services and exposing sensitive credentials. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.17.17, 3.18.11, 3.19.8, 3.20.4, and 3.21.2. This vulnerability was reported via the GitHub Bug Bounty program.

A command injection vulnerability was identified in GitHub Enterprise Server that allowed an attacker with an editor role in the Management Console to gain admin SSH access to the appliance via the actions-console docker container while setting a service URL. Exploitation of this vulnerability required access to the GitHub Enterprise Server instance and access to the Management Console with the editor role. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.12 and was fixed in versions 3.11.5, 3.10.7, 3.9.10, and 3.8.15. This vulnerability was reported via the GitHub Bug Bounty program.

A command injection vulnerability was identified in GitHub Enterprise Server that allowed an attacker with an editor role in the Management Console to gain admin SSH access to the appliance via nomad templates when configuring SMTP options. Exploitation of this vulnerability required access to the GitHub Enterprise Server instance and access to the Management Console with the editor role. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.12 and was fixed in versions 3.11.5, 3.10.7, 3.9.10, and 3.8.15. This vulnerability was reported via the GitHub Bug Bounty program https://bounty.github.com .

A command injection vulnerability was identified in GitHub Enterprise Server that allowed an attacker with an editor role in the Management Console to gain admin SSH access to the appliance when setting up an HTTP proxy. Exploitation of this vulnerability required access to the GitHub Enterprise Server instance and access to the Management Console with the editor role. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.12 and was fixed in versions 3.11.5, 3.10.7, 3.9.10, and 3.8.15. This vulnerability was reported via the GitHub Bug Bounty program https://bounty.github.com .

A command injection vulnerability was identified in GitHub Enterprise Server that allowed an attacker with an editor role in the Management Console to gain admin SSH access to the appliance when setting the username and password for collectd configurations. Exploitation of this vulnerability required access to the GitHub Enterprise Server instance and access to the Management Console with the editor role. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.12 and was fixed in versions 3.11.5, 3.10.7, 3.9.10, and 3.8.15. This vulnerability was reported via the GitHub Bug Bounty program https://bounty.github.com .

A command injection vulnerability was identified in GitHub Enterprise Server that allowed an attacker with an editor role in the Management Console to gain admin SSH access to the appliance via nomad templates when configuring audit log forwarding. Exploitation of this vulnerability required access to the GitHub Enterprise Server instance and access to the Management Console with the editor role. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.12 and was fixed in versions 3.11.5, 3.10.7, 3.9.10, and 3.8.15. This vulnerability was reported via the GitHub Bug Bounty program https://bounty.github.com .

A command injection vulnerability was identified in GitHub Enterprise Server that allowed an attacker with an editor role in the Management Console to gain admin SSH access to the appliance when configuring SAML settings. Exploitation of this vulnerability required access to the GitHub Enterprise Server instance and access to the Management Console with the editor role. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.12 and was fixed in versions 3.11.5, 3.10.7, 3.9.10, and 3.8.15. This vulnerability was reported via the GitHub Bug Bounty program https://bounty.github.com .

A command injection vulnerability was identified in GitHub Enterprise Server that allowed an attacker with an editor role in the Management Console to gain admin SSH access to the appliance when configuring GeoJSON settings. Exploitation of this vulnerability required access to the GitHub Enterprise Server instance and access to the Management Console with the editor role. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.13 and was fixed in versions 3.8.17, 3.9.12, 3.10.9, 3.11.7, and 3.12.1. This vulnerability was reported via the GitHub Bug Bounty program.

A path collision and arbitrary code execution vulnerability was identified in GitHub Enterprise Server that allowed container escape to escalate to root via ghe-firejail path. Exploitation of this vulnerability requires Enterprise Administrator access to the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise prior to 3.15 and was fixed in versions 3.14.3, 3.13.6, 3.12.11, and 3.11.17. This vulnerability was reported via the GitHub Bug Bounty program.

Summary

GitHub CLI incorrectly includes an authorization header in API requests to TUF repository mirrors via gh attestation, gh release verify, and gh release verify-asset commands.

Affected users:

- Authenticated github.com users who previously ran gh attestation commands, gh release verify, or gh release verify-asset: the github.com token was included in requests to tuf-repo.github.com, a GitHub Pages domain that is not a GitHub API endpoint. All authentication types are affected. - Users with GHENTERPRISETOKEN or GITHUBENTERPRISETOKEN set who previously ran gh attestation commands, gh release verify, or gh release verify-asset: the enterprise token was included in requests to external hosts tuf-repo-cdn.sigstore.dev and tmaproduction.blob.core.windows.net. These hosts are not operated by GitHub.

Details

The CLI uses a shared HTTP client with an authentication layer that automatically attaches tokens to outgoing requests. This layer lacks accurate host detection and can incorrectly attribute the target host, providing it with a token it should never receive.

Specifically, the host normalization logic collapses any .github.com subdomain to github.com, so a request to tuf-repo.github.com (a GitHub Pages site, not a GitHub API endpoint) is treated as a request to github.com and receives the user's github.com token. For hosts that don't match github.com or a known GHES instance at all, the resolver falls back to GHENTERPRISETOKEN if set.

The gh attestation, gh release verify and gh release verify-asset commands fetch data from several external hosts as part of their normal operation (TUF metadata from tuf-repo.github.com and tuf-repo-cdn.sigstore.dev, artifact bundles from Azure Blob Storage). Because these requests go through the same authenticated HTTP client, the token is sent to all of them.

Impact

Tokens were transmitted in HTTP headers to the listed hosts during normal gh attestation, gh release verify, and gh release verify-asset operations. There is no evidence that tokens were logged, retained, or accessed by unauthorized parties. If a token were captured, it would grant the same access as the token holder, potentially including private repositories, organization resources, or enterprise administration depending on token type and permissions.

Remediation and mitigation

1. Revoke authentication tokens used with the GitHub CLI: - Personal access tokens - GitHub CLI OAuth app 2. Upgrade gh to 2.93.0. 3. Review personal security logs and any relevant audit logs for actions associated with personal or enterprise accounts.

An URL redirection vulnerability was identified in GitHub Enterprise Server that allowed attacker-controlled redirects to leak sensitive authorization tokens. The repositorypages API insecurely followed HTTP redirects when fetching artifact URLs, preserving the authorization header containing a privileged JWT. An authenticated user could redirect these requests to an attacker-controlled domain, exfiltrate the Actions.ManageOrgs JWT, and leverage it for potential remote code execution. Attackers would require access to the target GitHub Enterprise Server instance and the ability to exploit a legacy redirect to an attacker-controlled domain. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.19 and was fixed in versions 3.19.2, 3.18.4, 3.17.10, 3.16.13, 3.15.17, and 3.14.22. This vulnerability was reported via the GitHub Bug Bounty program.

GitHub Kanban MCP Server is a Model Context Protocol (MCP) server for managing GitHub issues in Kanban board format and streamlining LLM task management. Version 0.3.0 of the MCP Server is written in a way that is vulnerable to command injection vulnerability attacks as part of some of its MCP Server tool definition and implementation. The MCP Server exposes the tool addcomment which relies on Node.js child process API exec to execute the GitHub (gh) command, is an unsafe and vulnerable API if concatenated with untrusted user input. As of time of publication, no known patches are available.

A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an attacker to extract sensitive environment variables from the instance through a timing side-channel attack against the notebook rendering service. When private mode was disabled, the notebook viewer followed HTTP redirects without revalidating the destination host, enabling an unauthenticated SSRF to internal services. By chaining this with regex filter queries against an internal API and measuring response time differences, an attacker could infer secret values character by character. Exploitation required that private mode be disabled and that the attacker be able to chain the instance's open redirect endpoint through an external redirect to reach internal services. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.14.26, 3.15.21, 3.16.17, 3.17.14, 3.18.8, 3.19.5, and 3.20.1. This vulnerability was reported via the GitHub Bug Bounty program.