Vulnerability · Published Sep 13, 2026 · Assigned by mitre
CVE-2026-90679
Medium 4.3
In plain English
A medium-severity security flaw in Forgejo from Forgejo. 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).
Official description
Forgejo 13.0.0 through 16.0.4, when "[federation] ENABLED = true" is set, has a spoofing issue that affects identity integrity but does not allow account takeover or content modification. It does not verify that the HTTP Signature on an incoming ActivityPub activity was produced by the key belonging to the actor named in the activity body. The signature verification in routers/api/v1/activitypub/reqsignature.go validates the request signature, but the inbox activity handlers subsequently read the acting identity from the attacker-controlled JSON body without binding it to the verified signing key. Additionally, the signed Digest header is not recomputed against the received request body. A remote attacker who hosts a single valid ActivityPub actor and keypair can therefore submit signature-valid activities attributed to any actor identity they name.
Affected products (as reported)
Weakness: CWE-348 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N