Signature algorithm downgrade via unadvertised CertificateVerify choice
Published Nov 21, 2025 · Updated Nov 21, 2025
Improper validation in wolfSSL 3.12.0 through 5.8.2 allows remote attackers to downgrade a TLS 1.3 CertificateVerify signature algorithm. In src/tls13.c, client-side CertificateVerify handling accepted the peer-selected algorithm without checking that it appeared in the SignatureAlgorithm extension sent by that client. Exploitation requires a wolfSSL TLS 1.3 client to connect to an attacker-controlled server and results in use of a weaker supported algorithm, such as ECDSA P-256 instead of ECDSA P-521.
Summary
What happened
Improper validation in wolfSSL 3.12.0 through 5.8.2 allows remote attackers to downgrade a TLS 1.3 CertificateVerify signature algorithm. In src/tls13.c, client-side CertificateVerify handling accepted the peer-selected algorithm without checking that it appeared in the SignatureAlgorithm extension sent by that client. Exploitation requires a wolfSSL TLS 1.3 client to connect to an attacker-controlled server and results in use of a weaker supported algorithm, such as ECDSA P-256 instead of ECDSA P-521.
The record
- CVE
- CVE-2025-11934
- Published
- Nov 21, 2025
- Updated
- Nov 21, 2025
- Vendor
- wolfSSL
- Product
- wolfSSL
- Classifications
- CWE-20, T1562.010
- Attack vector
- network
- Privileges
- admin
Timeline
How it unfolded
- Nov 21, 2025CVE publishedPublication date reported by the CVE source.
- Nov 21, 2025Record 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=v5.8.2
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
- TLS 1.3 CertificateVerify signature-algorithm PoCproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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