Gitea OAuth2 auto-linking lets attackers take over accounts
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA. Impact type from CWE-287.
Summary
Gitea from 0 before 28.3.0 is affected when ACCOUNT_LINKING is set to auto and registration is enabled. The link-account sign-up form selects the account to link by a user name or email typed into the form instead of the identity the OAuth2 provider asserts (CWE-639). An attacker with an account on a configured OAuth2 provider can submit another user's name, link their identity, and sign in as that user without its password, including as an administrator.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Description from the CNA
When `[oauth2_client].ACCOUNT_LINKING` is set to `auto` (not the default) and registration is enabled, the link-account sign-up form looked up the existing account to link by the user name or email submitted in the form instead of the identity asserted by the OAuth2 provider. An attacker with an account on a configured OAuth2 provider could submit another user's name, link their external identity to that Gitea account and be signed in as it without its password, including as an administrator. The link persisted for later sign-ins. Automatic linking now only happens when the existing account matches the provider's email or provider-derived user name; otherwise the account password is required.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
Upgrade Gitea to 28.3.0, the fixed version. The fix allows automatic linking only when the existing account matches the provider's email or provider-derived user name, and otherwise requires the account password.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
- Fix · CNA Gitea (Gitea) Fixed in 28.3.0
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Release ·
Gitea 28.3.0
20 records Highest priority Priority MEDIUM 3 MEDIUM, 17 LOW
Other records, highest priority first
- TI-2026-83601 Gitea public-only token can expose private OCI blobs through package mountsPriority MEDIUM 47
- TI-2026-83594 Gitea public-only token bypass exposes private repository jobsPriority MEDIUM 47
- TI-2026-83607 Gitea leaks private pull request details on project boardsPriority LOW 39
Timeline
- 2026-11-01 Threatist record created from CVE-2026-120263
- 2026-11-06 CVSS score added · CISA ADP
- 2026-11-06 CISA SSVC decision points changed
- 2026-11-06 Priority changed: LOW → MEDIUM
References
More Gitea vulnerabilities
- TI-2026-42785 Gitea before 1.27.1 allows remote code execution via the diffpatch API through Git hook installation. KEVCVSS 3.1CRITICAL 9.8
- TI-2026-42033 Improper authorization on OAuth sign-in callback silently re-enables administrator-disabled accounts CVSS 3.1CRITICAL 9.8
- TI-2026-40842 Privilege Escalation via Access Token Scope Escalation in API CVSS 3.1CRITICAL 9.8
- TI-2026-16922 Gitea Docker image trusts spoofable reverse-proxy headers by default CVSS 3.1CRITICAL 9.8
- TI-2026-42043 Team-repository linking endpoint bypasses the RepoAdminChangeTeamAccess organization setting CVSS 3.1CRITICAL 9.1
- TI-2026-40381 OIDC userinfo Endpoint Returns Identity Claims Without Enforcing API Token Scopes CVSS 3.1CRITICAL 9.1
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences