Signature validation bypass via signer-controlled validation time
Published Aug 3, 2026 · Updated Aug 3, 2026
Signature-validation bypass in Bouncy Castle Java S/MIME libraries allows remote attackers to validate back-dated signatures. SignedMailValidator.getSignatureTime() returns the signer-controlled CMS signingTime attribute, and validateSignatures() uses it as the PKIX path-validation date. An attacker with an expired or revoked signing key can choose a time before expiry or revocation, causing certificate and CRL checks to accept the signature without an RFC 3161 timestamp token.
Summary
What happened
Signature-validation bypass in Bouncy Castle Java S/MIME libraries allows remote attackers to validate back-dated signatures. SignedMailValidator.getSignatureTime() returns the signer-controlled CMS signingTime attribute, and validateSignatures() uses it as the PKIX path-validation date. An attacker with an expired or revoked signing key can choose a time before expiry or revocation, causing certificate and CRL checks to accept the signature without an RFC 3161 timestamp token.
The record
- CVE
- CVE-2026-59641
- Published
- Aug 3, 2026
- Updated
- Aug 3, 2026
- Vendor
- Legion of the Bouncy Castle Inc.
- Product
- Bouncy Castle Java
- Classifications
- CWE-345, T1553
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 3, 2026CVE publishedPublication date reported by the CVE source.
- Aug 3, 2026Record updatedLatest update available in the CVE record.
Exploitability
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Is a vulnerable build present?
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- Affected versionversion=0 <1.85
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What is affected?
Published CVSS scores
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Attacks
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Technologies
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