OAuth2 PKCE Bypass in Gitea

Publication date: 2026-07-03

Last updated on: 2026-07-03

Assigner: Gitea Limited

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.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-07-03

Last Modified

2026-07-03

Generated

2026-07-04

AI Q&A

2026-07-04

EPSS Evaluated

N/A

NVD

CVE-2026-26247

Affected Vendors & Products

Vendor	Product	Version / Range
gitea	gitea	to 1.25.5 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-284	The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.

Attack-Flow Graph

Executive Summary

This vulnerability affects Gitea versions before 1.25.5. It involves the OAuth2 PKCE S256 challenge method, which is not correctly persisted during the authorization process. As a result, the token exchange can occur without the expected verifier check.

Impact Analysis

Because the OAuth2 PKCE S256 challenge method is not properly enforced, an attacker could potentially exchange tokens without providing the correct verifier. This could lead to unauthorized access to protected resources or accounts.

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