CVE-2026-26247 Gitea OAuth2 PKCE S256 challenges are not enforced during token exchange
Attackers can bypass OAuth2 PKCE verification to obtain tokens without the correct verifier, potentially leading to unauthorized access.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-26247?
CVE-2026-26247 is a critical authentication bypass vulnerability in Gitea Open Source Git Server, published on 3 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Gitea versions before 1.25.5 do not persist the OAuth2 PKCE S256 challenge method correctly during authorization, allowing token exchange without the expected verifier check.
Weakness: CWE-284
Which versions are affected by CVE-2026-26247?
3 open source packages ship an affected version, including code.gitea.io/gitea.
| Package | Affected | Fixed in |
|---|---|---|
code.gitea.io/gitea Go | All versions | 1.25.5 |
code.gitea.io/gitea Go | All versions | 1.25.5 |
code.gitea.io/gitea Go | All versions | 1.25.5 |
How do I fix CVE-2026-26247?
Upgrade code.gitea.io/gitea to 1.25.5 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-26247 being exploited?
There is no known exploitation of CVE-2026-26247 in the wild and no public exploit code.
Sources
Also known as GHSA-m5ch-ppfx-xv3v, GO-2026-6342.