CVE-2026-109553
Gitea SSH certificate principal impersonation of other users
Gitea resolved the principals of an SSH certificate by searching the content of all stored public keys instead of only principal keys. When Gitea trusts a user certificate authority (SSH_TRUSTED_USER_CA_KEYS) and accepts arbitrary principals (SSH_AUTHORIZED_PRINCIPALS_ALLOW=anything), a user could register another user's public key line as their own principal, or a holder of a certificate signed by that authority could list it, and then authenticate as the owner of that key through the HTTP signature API and the built-in SSH server. Instances that do not trust a user certificate authority are not affected.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Gitea SSH certificate principal impersonation of other users
Gitea resolved the principals of an SSH certificate by searching the content of all stored public keys instead of only principal keys. When Gitea trusts a user certificate authority (SSH_TRUSTED_USER_CA_KEYS) and accepts arbitrary principals (SSH_AUTHORIZED_PRINCIPALS_ALLOW=anything), a user could register another user's public key line as their own principal, or a holder of a certificate signed by that authority could list it, and then authenticate as the owner of that key through the HTTP signature API and the built-in SSH server. Instances that do not trust a user certificate authority are not affected.
- Record
CVE-2026-109553- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-287
- Updated
- 2026-11-02
EUVDEUVD-2026-103983
Gitea resolved the principals of an SSH certificate by searching the content of all stored public keys instead of only principal keys. When Gitea trusts a user certificate authority (SSH_TRUSTED_USER_CA_KEYS) and accepts arbitrary principals (SSH_AUTHORIZED_PRINCIPALS_ALLOW=anything), a user could register another user's public key line as their own principal, or a holder of a certificate signed by that authority could list it, and then authenticate as the owner of that key through the HTTP signature API and the built-in SSH server. Instances that do not trust a user certificate authority are not affected.
- Record
EUVD-2026-103983- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-03
NVD
Gitea resolved the principals of an SSH certificate by searching the content of all stored public keys instead of only principal keys. When Gitea trusts a user certificate authority (SSH_TRUSTED_USER_CA_KEYS) and accepts arbitrary principals (SSH_AUTHORIZED_PRINCIPALS_ALLOW=anything), a user could register another user's public key line as their own principal, or a holder of a certificate signed by that authority could list it, and then authenticate as the owner of that key through the HTTP signature API and the built-in SSH server. Instances that do not trust a user certificate authority are not affected.
- Record
CVE-2026-109553- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-287
- Updated
- 2026-11-02
OSV
Gitea SSH certificate principal impersonation of other users
Gitea resolved the principals of an SSH certificate by searching the content of all stored public keys instead of only principal keys. When Gitea trusts a user certificate authority (SSH_TRUSTED_USER_CA_KEYS) and accepts arbitrary principals (SSH_AUTHORIZED_PRINCIPALS_ALLOW=anything), a user could register another user's public key line as their own principal, or a holder of a certificate signed by that authority could list it, and then authenticate as the owner of that key through the HTTP signature API and the built-in SSH server. Instances that do not trust a user certificate authority are not affected.
- Record
CVE-2026-109553- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-04
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| facts | EUVD, OSV | |
| first indexed | CVE List, EUVD, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-109553 is a high vulnerability (CVSS 7.5) in Gitea, published October 18, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.18%, the 7th percentile. No source names a fixed version.
References
github.com/go-gitea/gitea/security/advisories/GHSA-vcp6-2qc6-gvq3
blog.gitea.com/release-of-28.2.0
nvd.nist.gov/vuln/detail/CVE-2026-109553