CVE-2026-59641 S/MIME validator trusts signer-asserted signingTime for path validation
Attackers can bypass S/MIME signature validation by manipulating the signing time, undermining trust in signed messages.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-59641?
CVE-2026-59641 is a high-severity vulnerability in Bouncycastle Bc-Java, published on 3 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In Bouncy Castle for Java before 1.85, S/MIME validator trusts signer-asserted signingTime for path validation. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bcmail-fips and bcjmail-fips 1.0.7 (1.0.X series), 2.0.7 (2.0.X series) and 2.1.7 (2.1.X series).
Weakness: CWE-345
Which versions are affected by CVE-2026-59641?
It affects 4 products.
Products include Bouncycastle Bc-Java, Bouncycastle Bcjmail-Fips, Bouncycastle Bcmail-Fips, Bouncycastle Bouncy Castle for Java Lts.
How do I fix CVE-2026-59641?
Upgrade to a fixed version.
Is CVE-2026-59641 being exploited?
There is no known exploitation of CVE-2026-59641 in the wild and no public exploit code.
Other vulnerabilities in Bouncycastle Bc-Java
- CVE-2007-6721 Legion of the Bouncy Castle Java Cryptography API Bleichenbacher Oracle Vulnerability
- CVE-2018-1000613 Deserialization of Untrusted Data in Bouncy castle
- CVE-2026-58062 Stapled OCSP response accepted without binding to the checked certificate
- CVE-2026-59638 JSSE hostname verifier CN-fallback enabled by default despite documented opt-in
- CVE-2026-59650 MTI/A0 DH agreement exponentiates unvalidated peer value
Sources
Also known as CLEANSTART-2026-DJ23607, CLEANSTART-2026-QC33291, DEBIAN-CVE-2026-59641, GHSA-vgvx-fcjw-w4m8, UBUNTU-CVE-2026-59641.