CVE-2026-55437: Coder vulnerable to stored HTML injection via workspace agent logs in AgentLogLine component
Summary
The AgentLogLine dashboard component instantiated ansi-to-html without escapeXML: true and inserted the result via dangerouslySetInnerHTML so HTML embedded in workspace agent log lines was rendered as live markup. Server-side sanitization did not neutralize HTML metacharacters.
Note: Exploitation requires a victim to view attacker-controlled agent logs in the dashboard.
Impact
A user who could run a workspace could emit arbitrary HTML into agent logs; when another user, including an administrator, viewed the workspace page, it rendered in their session. Content Security Policy blocked inline scripts but an attacker could still inject a meta refresh redirect, style rules for UI redressing or CSS-based exfiltration or external img beacons. This required workspace-owner access and a victim viewing the page.
Patches
The fix enables escapeXML: true so HTML metacharacters are escaped before DOM insertion.
The fix was backported to all supported release lines:
| Release line | Patched version | |---|---| | 2.34 | v2.34.2 | | 2.33 | v2.33.8 | | 2.32 | v2.32.7 | | 2.29 (ESR) | v2.29.17 |
Workarounds
None.
Resources
- Fix: #25808
Credits
Coder would like to thank Anthropic's Security Team (ANT-2026-22449) for independently disclosing this issue!
Other sources
Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2, the AgentLogLine dashboard component instantiated ansi-to-html without escapeXML: true and inserted the result via dangerouslySetInnerHTML so HTML embedded in workspace agent log lines was rendered as live markup. Server-side sanitization did not neutralize HTML metacharacters. Exploitation requires a victim to view attacker-controlled agent logs in the dashboard. The fix in versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2 enables escapeXML: true so HTML metacharacters are escaped before DOM insertion. No known workarounds are available.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
go/github.com/coder/coder/v2to a version that resolves this vulnerability.Fixed in 2.29.17 - Upgrade
Upgrade
go/github.com/coder/coder/v2to a version that resolves this vulnerability.Fixed in 2.32.7 - Upgrade
Upgrade
go/github.com/coder/coder/v2to a version that resolves this vulnerability.Fixed in 2.33.8 - Upgrade
Upgrade
go/github.com/coder/coder/v2to a version that resolves this vulnerability.Fixed in 2.34.2 - Upgrade
Upgrade
Coderto a version that resolves this vulnerability.Fixed in 2.29.17 - Upgrade
Upgrade
Coderto a version that resolves this vulnerability.Fixed in 2.32.7 - Upgrade
Upgrade
Coderto a version that resolves this vulnerability.Fixed in 2.33.8 - Upgrade
Upgrade
Coderto a version that resolves this vulnerability.Fixed in 2.34.2 - Configuration
Ensure the AgentLogLine component instantiates ansi-to-html with escapeXML: true so HTML metacharacters in workspace agent log lines are escaped before being inserted via dangerouslySetInnerHTML.
AgentLogLine dashboard component (ansi-to-html) escapeXML = true
Event History
Frequently Asked Questions
What is the severity of CVE-2026-55437?
The severity of CVE-2026-55437 is medium with a score of 5.4.
What kind of vulnerability is associated with CVE-2026-55437?
CVE-2026-55437 is classified as an XSS (Cross-Site Scripting) vulnerability.
How do I fix CVE-2026-55437?
To fix CVE-2026-55437, ensure `ansi-to-html` is instantiated with `escapeXML: true` to prevent the risk of HTML rendering.
What component is affected by CVE-2026-55437?
The `AgentLogLine` dashboard component is affected by CVE-2026-55437.
What is the impact of exploiting CVE-2026-55437?
Exploitation of CVE-2026-55437 could allow an attacker to execute arbitrary HTML and JavaScript in the context of the user's session.