CVE-2026-63575 Legion of the Bouncy Castle Inc. CVE debrief

Who should care

Defenders responsible for the security of systems that use Bouncy Castle Inc. bc-csharp should assess exposure and prioritize verification and mitigation of this vulnerability. This includes operators, platform administrators, vulnerability management teams, and security teams who need to review and limit the use of PKCS#12 (PFX) files and PKCS#8 encrypted private keys that use PKCS#12 password-based encryption algorithms.

Why it matters

Defenders should care about CVE-2026-63575 because it is a denial-of-service vulnerability in Bouncy Castle Inc. bc-csharp that can be exploited through a specially crafted PKCS#12 (PFX) file or PKCS#8 encrypted private key, potentially leading to CPU exhaustion and system instability.

• CPU exhaustion through denial-of-service
• Potential for system instability or unavailability
• Need for verification of bc-csharp version in use
• Possible impact on system performance

Technical summary

The PKCS#12 key derivation (Pkcs12ParametersGenerator) in Bouncy Castle Inc. bc-csharp before version 2.7.0 has a loop with an unreachable exit condition. An attacker who can supply a PKCS#12 (PFX) file or a PKCS#8 encrypted private key that uses a PKCS#12 password-based encryption algorithm can cause CPU exhaustion through an iteration count of zero or below. This vulnerability can lead to denial-of-service and potential system instability. Defenders should prioritize verifying the version of bc-csharp in use and upgrading to version 2.7.0 or later to mitigate this vulnerability.

Defensive priority

Defenders should prioritize verifying the version of bc-csharp in use and upgrading to version 2.7.0 or later to mitigate this vulnerability.

Recommended defensive actions

• Verify the version of bc-csharp in use and upgrade to version 2.7.0 or later
• Review and limit the use of PKCS#12 (PFX) files and PKCS#8 encrypted private keys that use PKCS#12 password-based encryption algorithms
• Monitor for and restrict the supply of malicious PKCS#12 (PFX) files or PKCS#8 encrypted private keys
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record and NVD vulnerability detail page provide information on the vulnerability, including its description, CVSS score, and affected versions. The vulnerability exists in Bouncy Castle Inc. bc-csharp before version 2.7.0. Defenders should verify the version of bc-csharp in use and review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.