What’s Vulnerable › Vulnerabilities

CVE-2026-63575: PKCS#12 key derivation loops about 2^32 times on a zero or negative iteration count

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-02 · updated 2026-10-28
• Weakness: CWE-835

Description

Loop with unreachable exit condition in the PKCS#12 key derivation (Pkcs12ParametersGenerator) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows 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, to cause a denial of service through CPU exhaustion via an iteration count of zero or below, because the derivation loop ran until its counter equalled the count, so for such a count it wrapped through about 2^32 iterations before the MAC or the password could be checked. A 75-byte PFX file with a negative MacData iteration count kept Pkcs12Store.Load busy for many minutes.

Affected products

• Legion of the Bouncy Castle Inc. bc-csharp: before 2.7.0 — fixed in 2.7.0
• Legion of the Bouncy Castle Inc. bc-csharp: before 2.7.0 — fixed in 2.7.0

How to fix

Upgrade to a fixed version: Legion of the Bouncy Castle Inc. bc-csharp 2.7.0; Legion of the Bouncy Castle Inc. bc-csharp 2.7.0. Check the vendor advisory for mitigations.

References

• https://github.com/bcgit/bc-csharp/commit/0c7a6dfd64c4a479577e35a728a766721b79aba7
• https://github.com/bcgit/bc-csharp/commit/7c0ed15f9783c9595b1a53f3900136461fd944f4
• https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63575

Get alerted when CVE-2026-63575 or the next vulnerability affects your stack