GHSA-rm89-rhwj-9j92: Code Injection
Impact
An attacker who controls or tampers with an OpenAPI description can cause Kiota to emit attacker-controlled Java or PHP source outside a generated documentation comment. The affected sanitizers remove comment terminators rather than neutralizing them, allowing a terminator to reform from overlapping characters or from subsequent normalization. The Java sanitizer also removes non-ASCII characters after removing terminators, which can create a new terminator.
Exploitation requires a developer or build pipeline to generate a client from the malicious description and subsequently compile and load the Java output, or load the PHP output. Code executes in the consuming application's or build environment's security context, not merely because Kiota reads the description.
Affected versions
The affected NuGet packages are Microsoft.OpenApi.Kiota and Microsoft.OpenApi.Kiota.Builder. The Java normalization-order defect was introduced in version 0.5.0 and remains present through version 1.34.1, including the separate 1.29.1 security-backport release. The PHP delimiter-reformation variant is also present in version 1.34.1 and 1.29.1. Version 1.35.0 fixes both variants.
The package version range below reflects the Java defect; it does not assert that PHP generation existed in every version in that range.
Patches
Upgrade to Kiota 1.35.0 or later and regenerate affected clients. The fix neutralizes block-comment delimiters instead of deleting them, and performs Java delimiter neutralization after non-ASCII normalization.
- Fix: https://github.com/microsoft/kiota/pull/8017 - Fixed release: https://github.com/microsoft/kiota/releases/tag/v1.35.0
Workarounds
Until upgrading, generate clients only from trusted, integrity-protected OpenAPI descriptions. Review generated Java and PHP source before compiling, loading, or deploying it. Restrict the privileges and secrets available to generation and build environments.
Related advisories
This is distinct from PHP double-quoted string interpolation (GHSA-jqwh-526h-c92j) and C# XML documentation newline breakout (GHSA-3hrf-2gc2-mx32). Those fixes do not address Java/PHP block-comment delimiter reformation.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
nuget/Microsoft.OpenApi.Kiota.Builderto a version that resolves this vulnerability.Fixed in 1.35.0 - Upgrade
Upgrade
nuget/Microsoft.OpenApi.Kiotato a version that resolves this vulnerability.Fixed in 1.35.0 - Upgrade
Upgrade
Microsoft Kiotato a version that resolves this vulnerability.Fixed in 1.35.0 - Compensating control
Restrict the privileges and secrets available to client-generation and build environments.
- Compensating control
Review generated Java and PHP source before compiling, loading, or deploying it.
- Compensating control
Until upgrading, generate clients only from trusted, integrity-protected OpenAPI descriptions.
- Operational
Regenerate affected clients after upgrading Kiota.
Event History
Frequently Asked Questions
Who is exposed to this issue?
Teams that generate Java or PHP clients from OpenAPI descriptions they do not fully trust are exposed. The risk extends to developer workstations and build pipelines that compile and load generated Java output or load generated PHP output.
What must happen for an attacker-controlled description to result in code execution?
An attacker must be able to control or tamper with the OpenAPI description used for generation. A developer or pipeline must then generate the client and compile and load the Java output, or load the PHP output; reading the description with Kiota alone does not execute the code.
Which package versions should be upgraded?
Upgrade Microsoft.OpenApi.Kiota and Microsoft.OpenApi.Kiota.Builder to version 1.35.0. The Java issue affects versions 0.5.0 through 1.34.1, including 1.29.1, while the PHP variant is present in 1.34.1 and 1.29.1.
How can teams identify potentially affected workflows before upgrading?
Identify builds or developer workflows using either affected NuGet package to generate Java or PHP clients, then determine whether their OpenAPI descriptions can be controlled or modified by untrusted parties. Generated Java becomes relevant when it is compiled and loaded, and generated PHP when it is loaded.