IKEv2 pre-authentication Null Pointer Dereference in EAP code
Summary
| CVE | CVE-2026-77206 |
|---|---|
| State | PUBLISHED |
| Assigner | libreswan |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-13 22:18:24 UTC |
| Updated | 2026-10-16 19:55:59 UTC |
| Description | 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. |
Risk And Classification
Primary CVSS: v3.1 7.5 HIGH from d42dc95b-23f1-4e06-9076-20753a0fb0df
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.005180000 probability, percentile 0.427290000 (date 2026-10-16)
Problem Types: CWE-476 | CWE-476 CWE-476: Null Pointer Dereference
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | d42dc95b-23f1-4e06-9076-20753a0fb0df | Secondary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | CNA | CVSS | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | The Libreswan Project | Libreswan | affected 4.7 5.3.2 semver | Not specified |
| CNA | The Libreswan Project | Libreswan | affected 5.4 5.4 semver | Not specified |
| CNA | The Libreswan Project | Libreswan | unaffected 5.3.3 semver | Not specified |
| CNA | The Libreswan Project | Libreswan | unaffected 5.4.1 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| libreswan.org/security/CVE-2026-77206/CVE-2026-77206.txt | d42dc95b-23f1-4e06-9076-20753a0fb0df | libreswan.org | |
| libreswan.org/security/CVE-2026-77206 | d42dc95b-23f1-4e06-9076-20753a0fb0df | libreswan.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Claude (Anthropic) (en)
CNA: David Korczynski (ADA Logics Ltd) (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-08-05T00:00:00.000Z | Libreswan was notified of the issue via [email protected] |
| CNA | 2026-09-24T00:00:00.000Z | Advanced notice given to supported customers and distributions |
| CNA | 2026-10-05T00:00:00.000Z | Public announcement and release of libreswan 5.3.3 and 5.4.1 |
Solutions
CNA: Upgrade to libreswan 5.3.3 or 5.4.1 or later. Note that EAP was not functional in libreswan 5.3. If you need EAP support, use 5.4.1 or later. Patches are available at https://libreswan.org/security/CVE-2026-77206/
Workarounds
CNA: Apply the available patch or upgrade to a supported version. No configuration-based workaround is available.
Exploits
CNA: No known exploitation in the wild. Exploitation requires sending a malicious IKE_AUTH packet and does not require peer authentication.