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Improper Access ControlWeakness · CWE-284

CVE-2026-26247

CRITICAL · 9.1 CVSS v3.1 Published 2026-07-03
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available 7 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Gitea before 1.25.5 fails to correctly persist the OAuth2 PKCE S256 code challenge method during the authorization flow, allowing an attacker who intercepts an authorization code to exchange it for tokens without providing the correct code verifier, effectively bypassing the PKCE protection mechanism.

MitigationUpgrade Gitea to version 1.25.5 or later to receive the PKCE S256 persistence fix; if immediate upgrade is not possible, monitor for unauthorized OAuth2 token exchanges and review OAuth2 application grants for suspicious activity.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine installed Gitea version
    Run 'gitea --version' or check the version file in your Gitea installation directory
    Affected if The version number is less than 1.25.5
  2. Verify OAuth2 provider is enabled
    Review your Gitea configuration file (usually app.ini) for the [oauth2] section and ensure ENABLE is set to true
    Affected if OAuth2 authentication is enabled in the configuration
  3. List existing OAuth2 applications
    Navigate to Site Administration > OAuth2 Applications in the Gitea web interface or query the database for oauth2_application records
    Affected if One or more OAuth2 applications exist in your Gitea instance
  4. Audit OAuth2 authorization grants for anomalies
    Check the oauth2_authorization_grant table or review grant records via Site Administration > OAuth2 Grants for unexpected or unauthorized authorization entries
    Affected if There are authorization grants that were created without proper code_verifier validation or appear suspicious

Your environment is affected if you are running Gitea version 1.25.4 or earlier with OAuth2 authentication enabled and have OAuth2 applications configured.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch github.com →
Interim mitigation

Upgrade Gitea to version 1.25.5 or later to receive the PKCE S256 persistence fix; if immediate upgrade is not possible, monitor for unauthorized OAuth2 token exchanges and review OAuth2 application grants for suspicious activity.

Recommended fix High confidence

Gitea 1.25.5

  1. 1. Back up your current Gitea installation and database before upgrading.
  2. 2. Download Gitea version 1.25.5 from the official releases page at https://github.com/go-gitea/gitea/releases
  3. 3. Replace the existing Gitea binary with the new version 1.25.5 binary.
  4. 4. Ensure the new binary has appropriate execute permissions.
  5. 5. Restart the Gitea service to apply the update.
  6. 6. Verify the service is running correctly and test OAuth2 authentication flows to confirm the PKCE fix is working.

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,560
Get the patch applied

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,096.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-26247 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
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  • Version or environment caveats, and links to real fixes
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