Gitea SSH certificate principal impersonation of other users

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-109553
StatePUBLISHED
AssignerGitea
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-18 19:16:32 UTC
Updated2026-10-19 21:17:04 UTC
DescriptionGitea 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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from ADP

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

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED7.5HIGHCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary7.5HIGHCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Gitea Gitea affected 28.1.0 semver Not specified

References

ReferenceSourceLinkTags
github.com/go-gitea/gitea/pull/39847 88ee5874-cf24-4952-aea0-31affedb7ff2 github.com
github.com/go-gitea/gitea/security/advisories/GHSA-vcp6-2qc6-gvq3 88ee5874-cf24-4952-aea0-31affedb7ff2 github.com
github.com/go-gitea/gitea/releases/tag/v28.2.0 88ee5874-cf24-4952-aea0-31affedb7ff2 github.com
github.com/go-gitea/gitea/pull/39839 88ee5874-cf24-4952-aea0-31affedb7ff2 github.com
blog.gitea.com/release-of-28.2.0 88ee5874-cf24-4952-aea0-31affedb7ff2 blog.gitea.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: https://github.com/DshtAnger (en)

CNA: https://github.com/silverwind (en)

CNA: https://github.com/wxiaoguang (en)

CNA: https://github.com/bircni (en)

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