VulnerabilityPublished 21 Sep 2026Updated 30 Oct 2026

CVE-2026-74735: Linux kernel · l2tp: fix tunnel and session refcount leak on seq_file release

Source GCVE Database

Compare

Authoritative record:CVE-2026-74735· Medium

Not known to be exploited · fixed in ebe2774e956482dd3c70b8991f6f7654356339e6 : update Linux kernel when convenient.

Data as of 30 Oct 2026, 19:33 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · CVSS not yet scored by NVD

Thin evidence

One scorer or none

Patch: Available – fixed in ebe2774e956482dd3c70b8991f6f7654356339e6, c38b723858a51d6ca4e56470b9f1087f23276772, bdf83613781956cc39798ed08321f74ab0467f4d +5

Exploitation evidence

Disclosed: evidence found.
CVE published 26 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 30 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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-wf96-m5fp-jh8c

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected >=3.16.60 <3.17 >=4.16.6 <4.17	Fixed in ebe2774e956482dd3c70b8991f6f7654356339e6 c38b723858a51d6ca4e56470b9f1087f23276772 bdf83613781956cc39798ed08321f74ab0467f4d bd897e414451fb34dfdf08b31899180e5ab7149b 9006c116dd111d457bf5d074990210f70a4ad2c8 8c4fde01bcf91f22b9c7ded8c3e14addd7ddd500 4.17 3.17
LinuxLinux	Affected =4.17	Fixed in–

AI-suggested

A fix has been implemented in the Linux kernel to properly drop tunnel and session references when the relevant procfs or debugfs files are closed prematurely. Users should apply the official kernel updates that include this fix. No additional mitigation steps are indicated.

Description

A reference count leak vulnerability in the Linux kernel's L2TP implementation was fixed. The issue occurs when userspace closes certain procfs or debugfs files before reading to EOF, causing tunnel and session references to remain undropped. This can lead to resource leaks in kernel memory management related to L2TP tunnels and sessions.

Impact

The vulnerability causes a resource leak in kernel memory related to L2TP tunnel and session references. While it does not directly enable code execution or privilege escalation, the leak could degrade system stability or performance over time if exploited repeatedly or in high-load scenarios.

Summary

CVE-2026-74735 addresses a reference count leak in the Linux kernel's L2TP code. Specifically, in the functions pppol2tp_proc_open() and l2tp_dfs_seq_open(), iteration state is stored in seq_file private data to support multiple read() calls. If userspace closes /proc/net/pppol2tp or /sys/kernel/debug/l2tp/tunnels before reaching EOF, the tunnel and session references stored in the seq_file private data are not properly released. The fix ensures that any remaining references are dropped in the release functions pppol2tp_proc_release() and l2tp_dfs_seq_release() when the file is closed, preventing resource leaks.

References

Community reviews

Loading reviews…