CVE-2026-63578 PUBLISHED

Unbounded PBE iteration count when decrypting PKCS#8 private keys

Assigner: bcorg
Reserved: 16.07.2026 Published: 02.10.2026 Updated: 02.10.2026

Allocation of resources without limits in password-based private-key decryption (PbeUtilities.GenerateCipherParameters) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who can supply an encrypted private key, such as a PKCS#8 EncryptedPrivateKeyInfo or "ENCRYPTED PRIVATE KEY" PEM file, to cause a denial of service through CPU exhaustion via an iteration count close to 2^31, because the count is taken from the unauthenticated algorithm parameters without an upper bound and the key derivation runs before the password or the data can be checked. PKCS#5 PBES1 and PBES2 (PBKDF2), the PKCS#12 PBE algorithms and CMS password recipients (CmsPbeKey) are affected. Loading PKCS#12 files with Pkcs12Store is covered by CVE-2026-63572, and a zero or negative count with the PKCS#12 algorithms by CVE-2026-63575.

Metrics

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS Score: 7.1

Product Status

Vendor Legion of the Bouncy Castle Inc.
Product bc-csharp
Versions Default: unaffected
  • affected from 0 to 2.7.0 (excl.)

Credits

  • Discovered by Claude, Anthropic's AI assistant, and triaged by the Anthropic security team in collaboration with Anthropic Research. finder

References

Problem Types

  • CWE-770 Allocation of Resources Without Limits or Throttling CWE

Impacts

  • Denial of Service (CPU exhaustion)