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TI-2026-73733 Aliases CVE-2026-77206GHSA-37xg-hvw9-pr82

NULL pointer dereference in Libreswan IKEv2 EAP handling

Priority MEDIUM 40CWE-476Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 3 fixed, 4 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-476.

Summary

Libreswan versions 4.7 through 5.3.2 and 5.4 are affected. A fall-through in the IKEv2 state machine dereferences a NULL EAP state pointer (CWE-476) even when EAP is not configured. A remote attacker can send a malicious IKE_AUTH packet without authenticating, which crashes and restarts the pluto daemon. Repeated exploitation causes denial of service, and remote code execution is not possible.

Written with Claude Haiku 5.5 from the sources below · 2026-11-07

Description from the CNA

Libreswan's IKEv2 state machine has a null pointer dereference bug in the EAP handling code for authentication. As a result of inconsistency within the IKEv2 state machine code, this bug can be triggered by any IKEv2 connection, even if EAP is not configured at all. The error is caused by a fall-through where it incorrectly dereferences ike->sa.st_eap which is NULL. A malicious IKE_AUTH packet can trigger this bug, meaning the peer does not need to be authenticated. The bug results in a crash and restart of the pluto daemon. No remote code execution is possible. Continued exploitation can cause a denial of service.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00658 51st percentileScored 2026-11-07
Fix Partial libreswan (The Libreswan Project): 5.3.3, 5.4.1Red Hat: 3 advisoriesRed Hat: 3 fixed, 4 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
The Libreswan Projectlibreswan4.7 – 5.3.2; 5.4 – 5.45.3.3, 5.4.1Patch availableCNA
  • libreswan VendorThe Libreswan Project Affected 4.7 – 5.3.2; 5.4 – 5.4 Fixed in 5.3.3, 5.4.1 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:libreswan:libreswan:*:*:*:*:*:*:*:*——The Libreswan Project

Remediation

Libreswan 5.3.3 or 5.4.1 fixes the flaw, and Red Hat ships fixes in RHSA-2026:89748 for Red Hat Enterprise Linux AppStream (v. 9), RHSA-2026:90492 for Red Hat Enterprise Linux AppStream (v. 8) and RHSA-2026:95346 for Red Hat OpenShift Container Platform 4.22. The sources list no fixed version for Fast Datapath for RHEL 9, Red Hat Enterprise Linux 10, Red Hat OpenShift Container Platform 4 or Red Hat OpenShift Container Platform 5.

Written with Claude Haiku 5.5 from the sources below · 2026-11-07

  • Fix · CNA libreswan (The Libreswan Project) Fixed in 5.3.3, 5.4.1

Red Hat 3 advisories

  • RHSA-2026:95346 Released 2026-11-06 · Red Hat rating Critical
    OpenShift Container Platform 4.22.22 bug fix and security update
    • Red Hat OpenShift Container Platform 4.22 rhcos-aarch64-4.22.9.8.202611032353-0, rhcos-ppc64le-4.22.9.8.202611032353-0, rhcos-s390x-4.22.9.8.202611032353-0 +1
  • RHSA-2026:90492 Released 2026-10-26 · Red Hat rating Important
    libreswan security update
    • Red Hat Enterprise Linux AppStream (v. 8) libreswan-4.12-2.el8_10.7
  • RHSA-2026:89748 Released 2026-10-26 · Red Hat rating Important
    libreswan security update
    • Red Hat Enterprise Linux AppStream (v. 9) libreswan-4.15-11.el9_8

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Fast Datapath for RHEL 9AffectedNo fix yet
Red Hat Enterprise Linux 10AffectedNo fix yet
Red Hat OpenShift Container Platform 4AffectedNo fix yet
Red Hat OpenShift Container Platform 5AffectedNo fix yet
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2026:90492
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2026:89748
Red Hat OpenShift Container Platform 4.22Fixed RHSA-2026:95346
Not affected: 2 products
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7

Timeline

  1. 2026-10-13 Threatist record created from CVE-2026-77206
  2. 2026-10-14 Alias added: GHSA-37xg-hvw9-pr82
  3. 2026-10-14 Priority changed: MEDIUM → LOW
  4. 2026-10-16 CISA SSVC decision points changed
  5. 2026-10-25 EPSS moved to the 50th–90th percentile
  6. 2026-10-25 Priority changed: LOW → MEDIUM
  7. 2026-10-26 Fix available: RHSA-2026:89748 · Red Hat
  8. 2026-10-26 Fix available: Red Hat Enterprise Linux AppStream (v. 9) · Red Hat
  9. 2026-10-27 Fix available: Red Hat Enterprise Linux AppStream (v. 8) · Red Hat
  10. 2026-10-29 Fix available: RHSA-2026:90492 · Red Hat
  11. 2026-10-30 Affected versions changed · Red Hat
  12. 2026-11-07 Fix available: RHSA-2026:95346 · Red Hat
  13. 2026-11-07 Fix available: Red Hat OpenShift Container Platform 4.22 · Red Hat

References

Patch 1

Advisory 1

  • TI-2023-09114 Libreswan 4.9 allows remote attackers to cause a denial of service (assert failure and… CVSS 3.1MEDIUM 6.5
  • TI-2013-05949 Race condition in the libreswan.spec files for Red Hat Enterprise Linux (RHEL) and Fedora… CVSS 2.0HIGH 9.3
  • TI-2023-02152 Uncontrolled resource consumption in libreswan CVSS 3.1HIGH 7.5
  • TI-2026-37395 IKEv2 Denial of Service via RSA-SHA1 (PKCS#1 RSASSA-PKCS1-v1_5) authentication payload CVSS 3.1HIGH 8.1
  • TI-2026-37394 IKEv1 Denial of Service via RSA-SHA1 (PKCS#1 Version 1.5 Encrypted) authentication payload CVSS 3.1HIGH 8.1
  • TI-2023-14401 pluto in Libreswan before 4.11 allows a denial of service (responder SPI mishandling and… CVSS 3.1HIGH 7.5
See all 28 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences