# CVE-2026-63568: Bouncy Castle CMP/CRMF password-based MAC resource exhaustion

Source: https://junglewise.ai/threats/cve-2026-63568-allocation-of-resources-without-limits-or-throttling-in-the-cmp  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-02. Updated: 2026-10-05  
License: CC BY 4.0 with a link back

CVE-2026-63568 · Severity: info · Published 2026-10-02

Bouncy Castle is a cryptographic library used to handle security operations like certificate requests. A vulnerability allows an attacker to send specially crafted certificate requests that force the library to perform excessive hash computations, consuming CPU and causing the application to become unresponsive. No authentication is required to launch this attack.

Technologies: [Legion of the Bouncy Castle BouncyCastle.Cryptography](https://junglewise.ai/threats/technologies/legion-of-the-bouncy-castle-bouncycastle-cryptography). Vendors: [Legion of the Bouncy Castle](https://junglewise.ai/threats/vendors/legion-of-the-bouncy-castle).

## Quick answers

**Is CVE-2026-63568 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-63568 being exploited in the wild.

**How severe is CVE-2026-63568?** Informational severity, published 2 October 2026.

**Which products and versions are affected?** Legion of the Bouncy Castle BouncyCastle.Cryptography before 2.7.0.

**Is there a fix for CVE-2026-63568?** Yes: fixed in BouncyCastle.Cryptography 2.7.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-63568 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-63568?** Check whether you run Legion of the Bouncy Castle BouncyCastle.Cryptography at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in BouncyCastle.Cryptography 2.7.0

## Technical details

The PKMacBuilder component in Bouncy Castle's CMP/CRMF password-based MAC verifier lacks iteration-count enforcement by default. An attacker can craft a CMP message or CRMF certificate request with a PBMParameter declaring an extremely large iteration count (up to ~2^31), forcing ProtectedPkiMessage.Verify and CertificateRequestMessage.IsValidSigningKeyPop to perform that many hash iterations before validating the MAC, causing CPU exhaustion. The vulnerability only affects code paths not explicitly setting an iteration-count ceiling via the PKMacBuilder(IPKMacPrimitivesProvider, int) constructor.

## Affected products

- Legion of the Bouncy Castle BouncyCastle.Cryptography before 2.7.0

## Timeline

- 2026-10-02: disclosed

## References

- [https://www.nuget.org/packages/BouncyCastle.Cryptography](https://www.nuget.org/packages/BouncyCastle.Cryptography)
- [https://github.com/bcgit/bc-csharp/commit/10a9862fad04bb0c832a78b10e71d9818d6d1a63](https://github.com/bcgit/bc-csharp/commit/10a9862fad04bb0c832a78b10e71d9818d6d1a63)

## Related threats

- [Bouncy Castle Cryptography unbounded resource allocation in password-based key decryption](https://junglewise.ai/threats/cve-2026-63578-allocation-of-resources-without-limits-in-password-based-private)
- [Bouncy Castle improper certificate name-constraint validation](https://junglewise.ai/threats/cve-2026-63577-improper-certificate-validation-in-the-directoryname-name)
- [Bouncy Castle C# improper certificate validation in URI name constraints](https://junglewise.ai/threats/cve-2026-63576-improper-certificate-validation-in-pkixnameconstraintvalidator)
- [Bouncy Castle C# PKCS#12 key derivation denial of service](https://junglewise.ai/threats/cve-2026-63575-loop-with-unreachable-exit-condition-in-the-pkcs-12-key)
- [Bouncy Castle memory exhaustion in OpenPGP subpacket parsing](https://junglewise.ai/threats/cve-2026-63574-memory-allocation-with-excessive-size-value-in-the-openpgp)