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CVE-2026-58063 Legion of the Bouncy Castle Inc. CVE debrief

The CVE record for CVE-2026-58063 was published on 2026-08-03T03:16:45.773Z and has not been modified since then. The NVD entry is currently empty. This CVE is related to Bouncy Castle for Java before 1.85, Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before specific versions. The vulnerability involves BCFKS keystore load honouring unbounded KDF cost from untrusted files, potentially leading to performance degradation or denial-of-service conditions. Organizations should verify Bouncy Castle for Java versions in use and consider upgrading to a secure version. Defenders should also review KDF cost settings and monitor for suspicious activity related to keystore loads.

Vendor
Legion of the Bouncy Castle Inc.
Product
BC-JAVA
CVSS
MEDIUM 5.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-08-03
Original CVE updated
2026-08-03
Advisory published
2026-08-03
Advisory updated
2026-08-03

Who should care

Organizations using Bouncy Castle for Java library versions before 1.85, as well as those using Bouncy Castle for Java LTS before 2.73.12 and Bouncy Castle for Java FIPS (BC-FJA) before specific versions, should be aware of this vulnerability and take necessary actions to upgrade or mitigate the risk. This includes security teams, vulnerability management teams, and operators of systems that utilize Bouncy Castle for Java. Additionally, platform administrators and security personnel responsible for monitoring and incident response should be informed about the potential impacts of this vulnerability.

Technical summary

The Bouncy Castle for Java library before version 1.85 has a vulnerability in the BCFKS keystore load functionality, which honours unbounded KDF cost from untrusted files. This issue also affects Bouncy Castle for Java LTS before 2.73.12 and Bouncy Castle for Java FIPS (BC-FJA) before specific versions. The vulnerability has a CVSS score of 5.3, indicating a medium severity level. The unbounded KDF cost issue could potentially lead to performance degradation or denial-of-service conditions. Organizations using affected versions of Bouncy Castle for Java should prioritize upgrading to a secure version.

Defensive priority

Medium priority given the CVSS score of 5.3 and the potential for unbounded KDF cost issues.

Recommended defensive actions

  • Verify Bouncy Castle for Java version and upgrade to 1.85 or later if necessary.
  • Review and adjust KDF cost settings for BCFKS keystore loads.
  • Monitor for any suspicious activity related to keystore loads.
  • Perform a thorough review of the Bouncy Castle for Java library usage within the organization.
  • Check for any exposed systems that require compensating controls while remediation is scheduled.
  • Track exceptions and retest remediated assets.
  • Review relevant monitoring, detection, and logs for exposed assets that need extra review.

Evidence notes

The evidence for CVE-2026-58063 is limited; primary official records indicate Bouncy Castle for Java before 1.85 has an issue with BCFKS keystore load honouring unbounded KDF cost from untrusted files. Defenders should verify Bouncy Castle for Java versions in use, review KDF cost settings, and monitor for suspicious activity related to keystore loads. Additional verification tasks may be necessary based on specific deployment contexts.

Official resources

AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-08-03T03:16:45.773Z and has not been modified since then.