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VulnerabilityPublished

CVE-2026-59640: Legion of the Bouncy Castle BC-JAVA · Observable Discrepancy

Affects Legion of the Bouncy Castle BC-JAVASource CVE Database V5

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Not known to be exploited · CVSS 8.7 High : upgrade to 1.85 soon.

Data as of 31 Oct 2026, 20:20 UTC

CVSS 4.0 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 28% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 1.85, 2.73.12, 2.1.13 +2
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/U:Amber

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 3 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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 31 Oct 2026.

What to do

Upgrade BC-JAVA and bcpg to 1.85; BC-LTS-JAVA and bcpg-lts8on to 2.73.12; BC-FJA to 2.1.13, 2.0.13 or 1.0.13.

Affected software

ProductAffectedFixed in
Legion of the Bouncy Castle Inc.BC-JAVAAffected
  • <1.85
Fixed in
  • 1.85
Legion of the Bouncy Castle Inc.BC-LTS-JAVAAffected
  • >=2.73.0 <2.73.12
Fixed in
  • 2.73.12
Legion of the Bouncy Castle Inc.BC-FJAAffected
  • >=2.1.0 <2.1.13
Fixed in
  • 2.1.13
Legion of the Bouncy Castle Inc.BC-FJAAffected
  • >=2.0.0 <2.0.13
Fixed in
  • 2.0.13
Legion of the Bouncy Castle Inc.BC-FJAAffected
  • >=1.0.0 <1.0.13
Fixed in
  • 1.0.13
GitHubbcpgpkg:github/bcpgOther threatsAffected
  • <1.85
Fixed in
  • 1.85

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

No temporary or official fixes have been documented at this time.

Description

CVE-2026-59640 is a high-severity vulnerability in Bouncy Castle for Java (BC-JAVA) involving an OpenPGP CFB quick-check oracle on symmetric/session-key paths. This affects versions before 1.85, versions from 2.73.0 up to but not including 2.73.12, and certain FIPS series versions. The vulnerability is categorized under CWE-203 (Observable Discrepancy).

References

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