# CVE-2026-59641: Bouncy Castle for Java S/MIME signature validation time trust vulnerability

Source: https://junglewise.ai/threats/cve-2026-59641-bouncy-castle-for-java-s-mime-signature-validation-time-trust  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-03. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-59641 · Severity: medium · CVSS 5.3 · Published 2026-08-03

Bouncy Castle is a widely-used cryptographic library that processes digitally signed messages (S/MIME). The vulnerability allows attackers to forge or manipulate the signing timestamp in S/MIME messages, potentially leading to acceptance of expired certificates or signatures that should have been rejected. This could enable unauthorized access or allow an attacker to bypass security validations on signed content.

Technologies: [Bouncycastle Bouncy Castle For Java Lts](https://junglewise.ai/threats/technologies/bouncy-castle-for-java-lts). Vendors: [Bouncycastle](https://junglewise.ai/threats/vendors/bouncycastle).

## Quick answers

**Is CVE-2026-59641 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-59641 being exploited in the wild.

**How severe is CVE-2026-59641?** Medium severity, with a CVSS score of 5.3, published 3 August 2026.

**Which products and versions are affected?** Bouncycastle Bouncy Castle For Java Lts before 2.73.12.

**Is there a fix for CVE-2026-59641?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-59641 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-59641?** Check whether you run Bouncycastle Bouncy Castle For Java Lts at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in the S/MIME message validator component of Bouncy Castle for Java, which improperly trusts the signer-asserted signingTime attribute during certificate path validation. This allows an attacker to present a signing time that differs from the actual time of signature creation, potentially causing the validator to accept certificates that were expired or not yet valid at the actual time of signing. The flaw affects cryptographic validation logic and requires network-accessible S/MIME processing. Patches are available in versions 1.85 and later (standard), 2.73.12 and later (LTS), and 1.0.7, 2.0.7, and 2.1.7 respectively for the FIPS variants.

## Affected products

- Bouncycastle Bouncy Castle for Java before 1.85
- Bouncycastle Bouncy Castle for Java LTS before 2.73.12
- Bouncycastle Bouncy Castle for Java FIPS bcmail-fips and bcjmail-fips before 1.0.7 (1.0.X), before 2.0.7 (2.0.X), before 2.1.7 (2.1.X)

## Timeline

- 2026-08-03: disclosed

## References

- [https://www.bouncycastle.org/download/bouncy-castle-java/](https://www.bouncycastle.org/download/bouncy-castle-java/)
- [https://www.bouncycastle.org/download/bouncy-castle-java-lts/](https://www.bouncycastle.org/download/bouncy-castle-java-lts/)

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