CVE-2026-26247

Gitea OAuth2 PKCE S256 challenges are not enforced during token exchange

Published Jul 3, 2026 CVSS 3.1 · 9.1 Critical EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-m5ch-ppfx-xv3v Gitea OAuth2 PKCE S256 verifier bypass
History
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Gitea
Gitea gitea Open Source Git Server
Vendors & Products Gitea
Gitea gitea Open Source Git Server
Type Values Removed Values Added
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.
Title Gitea OAuth2 PKCE S256 challenges are not enforced during token exchange
Weaknesses CWE-284
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Gitea
Published
Updated
Jul 7, 2026, 4:59 PM
Reserved
Mar 3, 2026, 3:25 AM
Status
Deferred
Published
Jul 3, 2026, 9:16 PM
Modified
Oct 25, 2026, 3:10 PM