fixnx
highCVE-2026-50722

CVE-2026-50722 Libreswan Vulnerability

Libreswan, via the function RSA_authenticate_hash_signature_pkcs1_1_5_rsa(), did not correctly verify the DER encoding of the ASN.1 digest when the IKEv2 AUTH payload was encoded using RSASSA-PKCS1-v1_5 (RFC 8017). A remote attacker can use a variation on the Bleichenbacher attack to forge the AUTH payload when small public exponents are used (e.g., e=3), leading to impersonation. Additionally, a remote attacker, by encoding a shorter than expected hash in the AUTH payload, could trigger an assertion leading to denial-of-service. The daemon aborts and restarts; continued exploitation causes sustained denial of service. Remote code execution is not possible. X.509 certificate verifications of the remote IKE peer are not affected.

ProductLibreswan
CVSS8.1
EPSS0.00352
UpdatedJuly 14, 2026

Quick answer

Libreswan should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.

Who is affected

Affected versions

  • Libreswan 3.0 through 5.3

Fixed versions

  • Libreswan 5.3.1 or later
  • Vendor backported patch for CVE-2026-50722

How to fix it

CVE-2026-50722 affects Libreswan. The affected range is Libreswan 3.0 through 5.3. Update to Libreswan 5.3.1 or later, Vendor backported patch for CVE-2026-50722. Fix exposed systems first, especially where internet-facing services, admin panels, and trusted internal users can be reached. If abuse is suspected, review logs and rotate secrets that may have been exposed.

  1. Inventory every Libreswan install and note the exact version.
  2. Compare each install with the affected range: Libreswan 3.0 through 5.3.
  3. Update to Libreswan 5.3.1 or later, Vendor backported patch for CVE-2026-50722.
  4. If you cannot patch today, restrict internet-facing services, admin panels, and trusted internal users to trusted users and networks.
  5. Back up the current configuration before changing production systems.
  6. Review recent logs for crashes, strange admin actions, failed logins, or unexpected access.
  7. Rotate passwords, tokens, certificates, or keys if compromise is suspected.
  8. Document the change, owner, date, and final version.

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Verify the fix

  • Confirm the installed version now matches the fixed guidance: Libreswan 5.3.1 or later, Vendor backported patch for CVE-2026-50722.
  • Confirm old affected versions are no longer deployed: Libreswan 3.0 through 5.3.
  • Confirm internet-facing services, admin panels, and trusted internal users is limited to the smallest needed group.
  • Rerun the relevant Fixnx scan or internal security check after the change.
  • Save logs, screenshots, or package output as proof of the fix.

Related categories

Network SecurityRemote Code ExecutionDenial of ServiceCryptography

Trusted references

Source advisoryNVDSource advisoryNVDSource advisoryNVDSource advisoryNVDSource advisoryNVDSource advisoryNVD

FAQ

What is affected by CVE-2026-50722?

Libreswan versions listed as affected should be reviewed: Libreswan 3.0 through 5.3.

What should I fix first?

Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.

How do I confirm the fix worked?

Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.

How are Fixnx security risk categories chosen?

Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.