# CVE-2026-50722: Libreswan signature verification bypass and DoS in IKEv2 AUTH payload

Source: https://junglewise.ai/threats/cve-2026-50722-libreswan-signature-verification-bypass-and-dos-in-ikev2-auth  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-02. Updated: 2026-07-02  
License: CC BY 4.0 with a link back

CVE-2026-50722 · Severity: high · CVSS 8.1 · Published 2026-07-02

Libreswan is a widely used tool for establishing secure VPN connections. A vulnerability in how it handles certain cryptographic signatures allows a remote attacker to potentially bypass authentication or crash the service. This could lead to unauthorized access to the private network or a total loss of VPN connectivity for users.

## Quick answers

**Is CVE-2026-50722 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-50722 being exploited in the wild.

**How severe is CVE-2026-50722?** High severity, with a CVSS score of 8.1, published 2 July 2026.

**Which products and versions are affected?** The Libreswan Project libreswan <= 5.3.

**Is there a fix for CVE-2026-50722?** A patch was published on 2026-06-24: Public announcement and release of version 5.3.1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-50722 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-50722?** Check whether anything you run is named in the advisory. 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.

## Technical details

A vulnerability exists in the RSA_authenticate_hash_signature_pkcs1_1_5_rsa() function due to improper verification of the DER encoding of the ASN.1 digest in IKEv2 AUTH payloads. When RSASSA-PKCS1-v1_5 is used with small public exponents (e.g., e=3), a remote attacker can perform a Bleichenbacher-style attack to forge signatures and impersonate a peer. Additionally, providing a shorter-than-expected hash in the AUTH payload triggers a reachable assertion, causing the daemon to abort and restart, leading to a denial-of-service. This issue is fixed in Libreswan version 5.3.1.

## Affected products

- The Libreswan Project libreswan <= 5.3

## Timeline

- 2026-03-24: disclosed: Libreswan notified of the issue
- 2026-06-16: other: Advanced notice given to customers and distributions
- 2026-06-24: patched: Public announcement and release of version 5.3.1
- 2026-07-02: advisory: NVD publication date

## References

- [https://github.com/libreswan/libreswan](https://github.com/libreswan/libreswan)
- [https://libreswan.org/security/CVE-2026-50721/CVE-2026-50721.txt](https://libreswan.org/security/CVE-2026-50721/CVE-2026-50721.txt)
- [https://libreswan.org/security/CVE-2026-50722/](https://libreswan.org/security/CVE-2026-50722/)
- [https://libreswan.org/security/CVE-2026-50722/CVE-2026-50722.txt](https://libreswan.org/security/CVE-2026-50722/CVE-2026-50722.txt)
- [https://www.rfc-editor.org/rfc/rfc8017](https://www.rfc-editor.org/rfc/rfc8017)