CMS forgery via truncated AES-GCM tags
Published Jun 23, 2026 · Updated Jun 23, 2026
Improper CMS validation in GnuPG through 2.5.20 allows local users to forge AES-GCM-authenticated messages using short tags. gpgsm derives the authentication-tag length from the attacker-controlled CMS mac field and passes four-byte tags to libgcrypt instead of enforcing a 12-byte minimum. Successful forgery requires roughly four billion attempts, and the result compromises message integrity without disclosing plaintext or interrupting service.
Summary
What happened
Improper CMS validation in GnuPG through 2.5.20 allows local users to forge AES-GCM-authenticated messages using short tags. gpgsm derives the authentication-tag length from the attacker-controlled CMS mac field and passes four-byte tags to libgcrypt instead of enforcing a 12-byte minimum. Successful forgery requires roughly four billion attempts, and the result compromises message integrity without disclosing plaintext or interrupting service.
The record
- CVE
- CVE-2026-57062
- Published
- Jun 23, 2026
- Updated
- Jun 23, 2026
- Vendor
- The GnuPG Project
- Product
- GnuPG
- Classifications
- CWE-1284, T1553
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 23, 2026CVE publishedPublication date reported by the CVE source.
- Jun 23, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <=2.5.20
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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