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VulnerabilityPublished Updated

CVE-2026-53262: Linux kernel · l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl()

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 7.8 High · fixed in e251d4cdfc725c9e7d686161e3b775a0e7d95053 : patch Linux kernel soon.

Data as of 26 Oct 2026, 12:55 UTC

CVSS 3.1 base score
7.8High
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.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in e251d4cdfc725c9e7d686161e3b775a0e7d95053, a213a8950414c684999dcf03edeea6c46ede172e, 312ecea13b67797747eb9d4b9dab8d3846de6dfb +2
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 25 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ fd558d186df2c13a22455373858bae634a4795af, < e251d4cdfc725c9e7d686161e3b775a0e7d95053
Fixed in
  • e251d4cdfc725c9e7d686161e3b775a0e7d95053
LinuxLinuxAffected
  • ≥ fd558d186df2c13a22455373858bae634a4795af, < a213a8950414c684999dcf03edeea6c46ede172e
Fixed in
  • a213a8950414c684999dcf03edeea6c46ede172e
LinuxLinuxAffected
  • ≥ fd558d186df2c13a22455373858bae634a4795af, < 312ecea13b67797747eb9d4b9dab8d3846de6dfb
Fixed in
  • 312ecea13b67797747eb9d4b9dab8d3846de6dfb
LinuxLinuxAffected
  • ≥ fd558d186df2c13a22455373858bae634a4795af, < 78cdfdca88cbf731a92f3b9ee5427c633dd94e28
Fixed in
  • 78cdfdca88cbf731a92f3b9ee5427c633dd94e28
LinuxLinuxAffected
  • ≥ fd558d186df2c13a22455373858bae634a4795af, < 62f327e287cf7b595ae3f73ba72f5cd2a9e9f39f
Fixed in
  • 62f327e287cf7b595ae3f73ba72f5cd2a9e9f39f
LinuxLinuxAffected
  • =2.6.35
Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl() pppol2tp_ioctl() read sock->sk->sk_user_data directly without any locks or reference counting. If a controllable sleep was induced during copy_from_user() (e.g. via a userfaultfd page fault sleep), a concurrent socket close could trigger pppol2tp_session_close() asynchronously. This frees the l2tp_session structure via the l2tp_session_del_work workqueue. Upon resuming, the ioctl thread dereferences the stale session pointer, resulting in a Use-After-Free (UAF). Fix this by securely fetching the session reference using the RCU-safe, refcounted helper pppol2tp_sock_to_session(sk) on entry. This locks the session's refcount across the sleep. We structured the function to exit via standard err breaks, guaranteeing that l2tp_session_put() is cleanly called on all return paths to drop the reference. To preserve existing behavior we validate the session and its magic signature only for the specific L2TP commands that require it. This ensures that generic/unknown ioctls called on an unconnected socket still return -ENOIOCTLCMD and correctly fall back to generic handlers (e.g. in sock_do_ioctl()).

References

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