# CVE-2026-63574: Bouncy Castle memory exhaustion in OpenPGP subpacket parsing

Source: https://junglewise.ai/threats/cve-2026-63574-memory-allocation-with-excessive-size-value-in-the-openpgp  
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-2026-63574 · Severity: info · Published 2026-10-02

Bouncy Castle is a cryptographic library used to process digital signatures and OpenPGP keys. An attacker can supply a malformed OpenPGP key or signature that causes the library to attempt allocating up to 2 GB of memory when parsing the subpacket header, exhausting available memory and crashing applications that use the library.

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-2026-63574 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-63574 being exploited in the wild.

**How severe is CVE-2026-63574?** 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-2026-63574?** 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-2026-63574 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-63574?** 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 vulnerability exists in SignatureSubpacketsParser.ReadPacket and UserAttributeSubpacketsParser.ReadPacket, which parse OpenPGP subpacket headers using the five-octet length form without enforcing upper bounds or validating the declared length against the enclosing packet size. An attacker can craft an OpenPGP public key, certificate, or signature with a malicious subpacket header that declares an excessive allocation size; this requires no authentication or special preconditions. The result is denial of service via OutOfMemoryException or memory exhaustion. The fix is available in version 2.7.0.

## 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/986fb4892bb39f292ba0fd82eba11d2cbc503217](https://github.com/bcgit/bc-csharp/commit/986fb4892bb39f292ba0fd82eba11d2cbc503217)

## 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 RSA PKCS#1 v1.5 padding oracle in CMS key-transport](https://junglewise.ai/threats/cve-2026-63573-observable-discrepancy-in-the-cms-rsa-pkcs-1-v1-5-key-transport)