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CVE-2026-53262
l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl()
Published 2026-06-25 (4 months ago) by the Linux kernel CNA. Subsystem net/l2tp. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-53262 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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()).
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/l2tp/l2tp_ppp.c
- What this is
- PPP OVER L2TPMAINTAINERS section matched on net/l2tp/l2tp_ppp.c · Maintained
Show whether Debian builds this, per release
Not established. This site could not find the build rule for the affected file in the kernel trees Debian ships, so it has no answer about whether Debian compiles this code. Read that as unknown, never as absent.
- bookworm, trixie, forky, sid?
- ?
- not established - no Makefile entry for the affected file
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS
Signals
- Published
- 2026-06-25 (4 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.12%, higher than 1.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/l2tp
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.35 | 6.12.94 | 78cdfdca88cb |
| 2.6.35 | 6.18.36 | e251d4cdfc72 |
| 2.6.35 | 7.0.13 | 62f327e287cf |
| 2.6.35 | 7.1 | a213a8950414 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The vulnerable path is reached through a local `ioctl()` on a connected PPPoL2TP `AF_PPPOX` socket. Remote L2TP packets do not invoke `pppol2tp_ioctl()`.
- AC:LAttack complexity, low
- The attacker controls both sides of the race by blocking `copy_from_user()` in the ioctl thread and closing the same socket concurrently. No external victim state is required.
- PR:LPrivileges required, low
- A local unprivileged user can reach the PPPoL2TP socket/ioctl path; L2TP management also uses user-namespace admin permissions rather than requiring real init-namespace root. This is not remotely reachable without local code execution.
- UI:NUser interaction, none
- No victim action is required after the attacker runs local code. The attacker creates/connects the socket, issues the ioctl, and closes the socket.
- S:UScope, unchanged
- The impact is within the kernel security authority on the same system. It is not a VM escape, IOMMU bypass, or cross-authority boundary violation.
- C:HConfidentiality impact, high
- This is a kernel heap use-after-free of `struct l2tp_session`, and the resumed ioctl can read from reclaimed/faked session and tunnel data before copying results to userspace. Per conservative kernel UAF scoring, this supports high confidentiality impact.
- I:HIntegrity impact, high
- Kernel UAFs with attacker-controlled timing and heap reuse can be leveraged beyond a simple stale read, including corruption or control-flow primitives. When uncertain, the higher severity option is appropriate.
- A:HAvailability impact, high
- At minimum, dereferencing the stale session or tunnel pointer can trigger a kernel oops or panic. The attacker can repeatedly trigger the race locally.