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CVE-2026-104445 – Authentication Bypass (Federated Entry Deletion/Overwrite) – YesWiki before 4.6.7

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Summary

CVE-2026-104445 is an authentication bypass vulnerability (CWE-290) in YesWiki’s ActivityPub inbox implementation, affecting all versions prior to 4.6.7. The flaw lets any unauthenticated attacker who controls an ActivityPub keypair delete or overwrite federated wiki entries belonging to other actors. The issue carries a CVSS v3.1 base score of 8.2 (High) and a CVSS v4.0 base score of 8.8 (High), and requires no authentication or user interaction to exploit remotely.

Technical details

  • Root cause: YesWiki’s ActivityPub inbox correctly verifies the cryptographic HTTP signature on an incoming activity, but never binds the verified signer identity to the actor claimed inside the activity body — the two are checked independently and never compared.
  • Trigger conditions: An attacker sends a validly signed Delete or Update ActivityPub activity to the inbox endpoint, referencing a mirrored entry’s sourceUrl. Because the signer-to-actor binding is never enforced, the activity is processed as if it came from the entry’s legitimate owner.
  • Attack vector: Network — the inbox endpoint is reachable without any YesWiki account or administrative privileges. The attacker only needs any valid ActivityPub keypair, not one belonging to the targeted actor.
  • Impact: Unauthenticated deletion or overwrite of other actors’ federated/mirrored wiki entries, resulting in a high integrity impact and a lower-severity availability impact, with no confidentiality impact.

Affected software

  • YesWiki, all versions prior to 4.6.7
  • Fixed in YesWiki 4.6.7

Severity

  • CVSS v3.1 Base Score: 8.2 (High) — Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
  • CVSS v4.0 Base Score: 8.8 (High) — Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N

Mitigation and recommended actions

  • Immediate: Upgrade all YesWiki installations to version 4.6.7 or later, which binds the verified HTTP signature signer to the claimed activity actor before processing Delete/Update operations.
  • If patching is not immediately possible: Restrict or disable public access to the ActivityPub inbox endpoint at the network or reverse-proxy layer until the upgrade can be applied, and monitor for unexpected deletions or overwrites of federated/mirrored entries as an indicator of attempted exploitation.

References

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