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Vulnerability · Published Oct 18, 2026 · Assigned by Gitea

CVE-2026-109553Gitea SSH certificate principal impersonation of other users

High 7.5

In plain English

A high-severity improper authentication in Gitea from Gitea. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 7% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.2%top 93.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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.

Affected products (as reported)

VendorProductVersions
Gitea Gitea 0 – through 28.1.0

Weakness: CWE-287 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

References