VulnerabilityPublished 19 Jul 2026Updated 13 Aug 2026

CVE-2026-64119: Linux kernel · l2tp: use list_del_rcu in l2tp_session_unhash

Source GCVE Database

Not known to be exploited · CVSS 5.5 Medium.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

5.5Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 1% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 19 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-pjh2-pg7v-jm22

What to do

AI-suggested

A fix is available that replaces list_del_init() with list_del_rcu() in l2tp_session_unhash(). Users should update their Linux kernel to a version that includes this fix. Since no vendor advisory or patch links are provided, check the Linux kernel mailing lists or distribution security advisories for the official patch and update instructions. Until patched, avoid running untrusted code with CAP_NET_ADMIN in user namespaces on hosts with the l2tp_core module loaded.

Description

A medium severity vulnerability in the Linux kernel's L2TP implementation allows an unprivileged local user with CAP_NET_ADMIN in a user namespace to indefinitely pin a host CPU. This occurs due to improper list deletion in l2tp_session_unhash(), causing a CPU to be wedged in a loop with BH and preemption disabled, stalling RCU grace periods and preventing thread termination. The issue is fixed by replacing list_del_init() with list_del_rcu() to safely remove sessions from the session list without disrupting RCU readers.

Impact

An unprivileged local user with CAP_NET_ADMIN in a network namespace can cause a host CPU to be pinned indefinitely, effectively causing a denial of service by stalling RCU grace periods and preventing the affected kernel thread from being killed promptly. There is no impact on confidentiality or integrity, but availability is severely affected.

Summary

The vulnerability in the Linux kernel's L2TP subsystem arises from the use of list_del_init() in l2tp_session_unhash() to remove a session from tunnel->session_list. This list is concurrently traversed under RCU read lock by l2tp_session_get_by_ifname(). Because list_del_init() leaves the deleted entry's next/prev pointers self-referential, the list traversal loops indefinitely inside strcmp() with bottom halves and preemption disabled, causing the CPU to be pinned indefinitely. The attacker requires CAP_NET_ADMIN in the network namespace, achievable from an unprivileged sandbox with user namespaces. The fix replaces list_del_init() with list_del_rcu(), ensuring safe removal of the session from the list while maintaining consistent pointers for in-flight readers until the session is freed with kfree_rcu().

References

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