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Maniphest T7904

GnuPG may downgrade digest algorithm to SHA1
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Description

GnuPG may downgrade the message digest algorithm to insecure SHA1 algorithm during signature checking due to reading from uninitialized memory.

Reported-by: 49016 and Liam (two-heart)

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Event Timeline

• gniibe created this task.Nov 4 2025, 6:45 AM
• gniibe created this object in space Restricted Space.
• gniibe created this object with visibility "g10code (Project)".
• gniibe created this object with edit policy "g10code (Project)".

Fixed in rGdb9705ef594d: gpg: Avoid potential downgrade to SHA1 in 3rd party key signatures.

• werner triaged this task as High priority.Nov 4 2025, 1:26 PM
• gniibe mentioned this in Unknown Object (Maniphest Task).Nov 10 2025, 2:51 AM
• werner changed the task status from Open to Testing.Nov 19 2025, 5:53 PM
• werner shifted this object from the Restricted Space space to the S1 Public space.
• werner updated the task description. (Show Details)
• werner changed the visibility from "g10code (Project)" to "Public (No Login Required)".
• werner changed the edit policy from "g10code (Project)" to "Contributor (Project)".
• werner removed a project: g10code.
thesamesam added a subscriber: thesamesam.Fri, Dec 26, 8:49 PM
• werner mentioned this in T8001: Release GnuPG 2.4.9.Tue, Dec 30, 1:49 PM
• werner closed this task as Resolved.Fri, Jan 9, 11:01 AM
• werner claimed this task.
• werner added a subscriber: • werner.

Note that for exploiting this bug a second preimage attack for SHA-1 is required. This kind of attack on SHA1 is not yet possible.