Gitea: Unauthenticated ReDoS via CODEOWNERS pattern matching allows denial of service

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-58421: 0.40% estimated exploitation activity in the next 30 days; percentile 33.91 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

This issue has been found by a security agent and review by myself. Gitea's CODEOWNERS feature uses the regexp2 library to match file paths against ownership rules. User-supplied patterns are passed directly to regexp2.Compile with no sanitisation and no match timeout. This allows an attacker to write a pattern that causes the regex engine to backtrack exponentially when evaluated against a crafted file path. Who can trigger it Any registered user on the instance. The attacker needs only: 1. A repository they own (created via normal signup) 2. A CODEOWNERS file on the default branch containing malicious patterns 3. A pull request branch containing a file with a crafted name No elevated permissions, no admin access, no existing repositories required. How it is triggered The attacker pushes a CODEOWNERS file containing repeated instances of a catastrophic backtracking pattern (e.g. (a+)+ @attacker) and opens a pull request from a branch that contains a file named with a long string of…

Published by the source

27 Jul 2026, 15:32 UTC

Last modified by the source

27 Jul 2026, 17:00 UTC

Source last checked

26 Oct 2026, 15:27 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-v96j-25gv-g2w9

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GO-2026-6077

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# Patch Next advisory brief: CVE-2026-58421

Advisory: Gitea: Unauthenticated ReDoS via CODEOWNERS pattern matching allows denial of service
IDs: CVE-2026-58421, GHSA-v96j-25gv-g2w9
Record: https://patchnext.com/advisories/cve-2026-58421 (revision 2, source checked 26 Oct 2026, 15:27 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: code.gitea.io/gitea 1.26.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go code.gitea.io/gitea: affected <= 1.26.2; fixed in 1.26.4

## Suggested inspection (read-only)
- Go code.gitea.io/gitea: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on code.gitea.io/gitea.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6077 (OSV record GO-2026-6077 lists affected ranges: Go code.gitea.io/gitea >=0 <1.26.4 (fixed))
- Verified: https://github.com/advisories/GHSA-v96j-25gv-g2w9 (GitHub-reviewed advisory GHSA-v96j-25gv-g2w9 lists affected ranges: Go code.gitea.io/gitea >=0 <=1.26.2)

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