FKIE_CVE-2026-109553

Vulnerability from fkie_nvd - Published: 2026-10-18 19:16 - Updated: 2026-10-19 21:17
Severity
7.5 (High) - CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
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.
References
88ee5874-cf24-4952-aea0-31affedb7ff2https://blog.gitea.com/release-of-28.2.0/
88ee5874-cf24-4952-aea0-31affedb7ff2https://github.com/go-gitea/gitea/pull/39839
88ee5874-cf24-4952-aea0-31affedb7ff2https://github.com/go-gitea/gitea/pull/39847
88ee5874-cf24-4952-aea0-31affedb7ff2https://github.com/go-gitea/gitea/releases/tag/v28.2.0
88ee5874-cf24-4952-aea0-31affedb7ff2https://github.com/go-gitea/gitea/security/advisories/GHSA-vcp6-2qc6-gvq3
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "packageName": "gitea.dev",
          "product": "Gitea",
          "vendor": "Gitea",
          "versions": [
            {
              "lessThanOrEqual": "28.1.0",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "source": "88ee5874-cf24-4952-aea0-31affedb7ff2"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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\u0027s 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."
    }
  ],
  "id": "CVE-2026-109553",
  "lastModified": "2026-10-19T21:17:04.780",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.6,
        "impactScore": 5.9,
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-109553",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-10-19T20:19:01.147709Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-10-18T19:16:32.997",
  "references": [
    {
      "source": "88ee5874-cf24-4952-aea0-31affedb7ff2",
      "url": "https://blog.gitea.com/release-of-28.2.0/"
    },
    {
      "source": "88ee5874-cf24-4952-aea0-31affedb7ff2",
      "url": "https://github.com/go-gitea/gitea/pull/39839"
    },
    {
      "source": "88ee5874-cf24-4952-aea0-31affedb7ff2",
      "url": "https://github.com/go-gitea/gitea/pull/39847"
    },
    {
      "source": "88ee5874-cf24-4952-aea0-31affedb7ff2",
      "url": "https://github.com/go-gitea/gitea/releases/tag/v28.2.0"
    },
    {
      "source": "88ee5874-cf24-4952-aea0-31affedb7ff2",
      "url": "https://github.com/go-gitea/gitea/security/advisories/GHSA-vcp6-2qc6-gvq3"
    }
  ],
  "sourceIdentifier": "88ee5874-cf24-4952-aea0-31affedb7ff2",
  "vulnStatus": "Awaiting Analysis"
}



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