CVE-2026-59641: Legion of the Bouncy Castle BC-JAVA · Insufficient Verification of Data Authenticity
Affects Legion of the Bouncy Castle BC-JAVASource CVE Database V5
Not known to be exploited · CVSS 8.7 High : upgrade to 1.85 soon.
Data as of 31 Oct 2026, 08:20 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 1.85, 2.73.12, 2.1.7 +2
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/U:AmberExploitation evidence
Disclosed: evidence found.
CVE published 3 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Upgrade BC-JAVA and bcmail to 1.85; BC-LTS-JAVA and bcmail-lts8on to 2.73.12; BC-FJA to 2.1.7, 2.0.7 or 1.0.7.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Legion of the Bouncy Castle Inc.BC-JAVA | Affected
| Fixed in
|
| Legion of the Bouncy Castle Inc.BC-LTS-JAVA | Affected
| Fixed in
|
| Legion of the Bouncy Castle Inc.BC-FJA | Affected
| Fixed in
|
| Legion of the Bouncy Castle Inc.BC-FJA | Affected
| Fixed in
|
| Legion of the Bouncy Castle Inc.BC-FJA | Affected
| Fixed in
|
| Legion of the Bouncy Castle Inc.BC-FJA | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
If you cannot patch yet, users should exercise caution when validating S/MIME signatures with affected versions of BC-JAVA. Monitoring vendor communications for updates is recommended.
Description
CVE-2026-59641 is a high-severity vulnerability in Legion of the Bouncy Castle Inc.'s BC-JAVA library. The issue involves insufficient verification of data authenticity in the S/MIME validator, which trusts the signer-asserted signingTime during path validation. This affects versions of BC-JAVA before 1.85 and versions from 2.73.0 up to but not including 2.73.12, including certain FIPS variants. The vulnerability has a CVSS 4.0 score of 8.7, indicating a significant security risk. There are no known exploits in the wild at this time.
References
- github.com/bcgit/bc-java/wiki/CVE-2026-59641 (opens in a new tab)
- github.com/bcgit/bc-java/commit/2f81b22d559b3a1b026388e1ca78dd547384def8 (opens in a new tab)
- github.com/bcgit/bc-java/commit/fd89fe918b37fea1c71e95fae50284a325b09721 (opens in a new tab)
- github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9059641 (opens in a new tab)