Vulnerability advisory

CVE-2026-26247

Gitea OAuth2 PKCE S256 challenges are not enforced during token exchange

Published Jul 3, 2026Updated Oct 28, 2026OSV record ↗

Also known as GHSA-m5ch-ppfx-xv3vGO-2026-6342

Severity

CVSS 3.xCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected versions

Repository

Affected commits	Fixed by commit
GIT github.com/go-gitea/gitea ↗
All commits before f913d90ab664c1deccdfbe8c563abb13e897d62b	`f913d90ab664c1deccdfbe8c563abb13e897d62b`
Also listed as affected (44) `v1.25.4` `v1.25.3` `v1.25.2` `v1.25.1` `v1.25.0` `v1.25.0-rc0` `v1.26.0-dev` `v1.25.0-dev` `v1.24.0-dev` `v1.22.0-rc1` `v1.23.0-dev` `v1.22.0-rc0` `v1.21.0-rc0` `v1.22.0-dev` `v1.20.0-rc0` `v1.21.0-dev` `v1.20.0-dev` `v1.19.0-rc0` `v1.18.0-rc0` `v1.19.0-dev` `v1.18.0-dev` `v1.17.0-dev` `v1.16.0-rc1` `v1.15.0-rc1` `v1.16.0-dev` `v1.15.0-dev` `v1.14.0-dev` `v1.13.0-dev` `v1.12.0-dev` `v1.10.5` `v1.11.0-rc1` `v1.10.0-rc1` `v1.11.0-dev` `v1.9.0-rc1` `v1.10.0-dev` `v1.9.0-dev` `v1.7.0-dev` `v1.6.0-rc1` `v1.6.0-dev` `v1.5.0-rc1` `v1.5.0-dev` `v1.1.0` `v1.0.0` `v0.9.99`

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.

CVE-2026-26247

Affected versions

Repository

Description

References