CVE-2026-52796 Overview
CVE-2026-52796 affects Gogs, an open source self-hosted Git service. Versions prior to 0.14.3 contain a flaw in the issue index pattern rendering logic. A specially crafted pattern triggers a runtime panic in RenderIssueIndexPattern, producing a denial of service condition. Any repository page containing an issue index reference such as #1 becomes unavailable once the malicious pattern is set. The maintainers fixed the issue in version 0.14.3.
Critical Impact
Authenticated users with permission to configure repository issue patterns can render affected pages permanently unavailable until administrators intervene.
Affected Products
- Gogs versions prior to 0.14.3
- Self-hosted Gogs Git service instances
- Repositories with configurable issue index patterns
Discovery Timeline
- 2026-06-24 - CVE-2026-52796 published to NVD
- 2026-06-25 - Last updated in NVD database
Technical Details for CVE-2026-52796
Vulnerability Analysis
The flaw resides in internal/markup/markup.go within the RenderIssueIndexPattern function. The function expands a configurable template using com.Expand, which does not safely validate template syntax. When the configured pattern contains an opening brace { but no matching closing brace }, strings.Index(template, "}") returns -1. The subsequent slice operation template[:-1] triggers a Go runtime panic.
This vulnerability falls under [CWE-1336] (Improper Neutralization of Special Elements Used in a Template Engine). The panic propagates up through the rendering pipeline, breaking any page that attempts to expand an issue reference such as #1.
Root Cause
The root cause is missing input validation on the issue index pattern template. The rendering function assumes well-formed templates with matched braces. It does not check the return value of strings.Index before performing slice arithmetic. An attacker who sets a malformed template forces a negative index slice, which Go treats as a runtime panic rather than a recoverable error.
Attack Vector
An authenticated user with rights to configure a repository's external issue tracker pattern submits a template containing an unmatched { character. After saving the pattern, any subsequent request that renders content with an issue reference triggers the panic. The affected pages remain unavailable until an administrator corrects or removes the malicious pattern. User interaction is required to trigger rendering on affected pages.
The vulnerability is described in prose because no public proof-of-concept code was identified. See the GitHub Security Advisory for additional technical context.
Detection Methods for CVE-2026-52796
Indicators of Compromise
- Gogs application logs containing Go runtime panic traces referencing RenderIssueIndexPattern or internal/markup/markup.go
- HTTP 500 responses on repository pages that contain issue references such as #1
- Repository configuration changes setting an external issue tracker pattern containing an unmatched { character
Detection Strategies
- Monitor Gogs server logs for repeated panic stack traces tied to markup rendering
- Audit recent changes to repository settings, specifically external tracker URL formats and issue index patterns
- Correlate authenticated user activity with subsequent rendering failures on affected repositories
Monitoring Recommendations
- Forward Gogs application and reverse proxy logs to a centralized logging or SIEM platform for panic pattern alerting
- Track HTTP 5xx error rates per repository to identify localized rendering failures
- Alert on configuration changes to issue pattern templates by non-administrative accounts
How to Mitigate CVE-2026-52796
Immediate Actions Required
- Upgrade Gogs to version 0.14.3 or later, which contains the fix for RenderIssueIndexPattern
- Audit existing repository configurations for malformed issue index patterns and remove or correct them
- Restrict repository administrative permissions to trusted users until patching completes
Patch Information
The vulnerability is fixed in Gogs version 0.14.3. Administrators should review the GitHub Security Advisory GHSA-4j89-2c4f-44c6 for upgrade guidance and release notes.
Workarounds
- Manually inspect and reset any repository issue index pattern containing an unmatched { character
- Limit who can modify external tracker settings on each repository to reduce the attack surface
- Monitor application logs for panic conditions and restart the Gogs service if pages become unavailable
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
