Gitea OAuth2 PKCE S256 Verifier Bypass: Early Warning
- Severity
- HIGH
- Affected component
- gitea (go)
- Affected versions
- < 1.25.5
- Patched version
- 1.25.5
An early warning has been issued for a potential vulnerability in Gitea versions before 1.25.5. This issue involves the OAuth2 PKCE S256 verifier bypass, which could allow unauthorized token exchange.
What happened
Gitea versions before 1.25.5 reportedly do not correctly persist the OAuth2 PKCE S256 challenge method during authorization. This oversight allows for token exchange without the expected verifier check, potentially exposing systems to unauthorized access. The issue was first flagged on July 3, 2026, and is currently under investigation. There is no evidence of this vulnerability being exploited in the wild at this time.
Users of Gitea should assess their exposure by checking the version of Gitea they are running. Any instance running a version before 1.25.5 is potentially vulnerable. It is recommended to upgrade to version 1.25.5 or later to mitigate this risk.
What to do about it
- Check the version of Gitea currently in use.
- Upgrade to Gitea version 1.25.5 or later to address the vulnerability.
- Monitor the primary sources for updates on this issue.
- Review OAuth2 configurations and ensure proper security measures are in place.
How 0Day would have caught this
gitea is anywhere in your dependency tree, the engineers who own the affected repositories get a push alert the moment it is flagged — no manual audit to remember to run.Read how this differs from waiting on a scanner to catch a known advisory, or see the exact, read-only access 0Day needs to do this for an organization.
Frequently asked questions
Am I affected?
If you are using Gitea versions before 1.25.5, you may be affected by this vulnerability.
What should I do right now?
Upgrade to Gitea version 1.25.5 or later as soon as possible.
Has this vulnerability been exploited in the wild?
There is no confirmed evidence of this vulnerability being exploited in the wild at this time.