# CVE-2026-23072: l2tp: Fix memleak in l2tp_udp_encap_recv().

> A memory leak in the Linux kernel L2TP module allows attackers to exhaust system memory, causing denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Feb 2026
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2026-23072, DEBIAN-CVE-2026-23072, GHSA-fm5m-5cr7-5q35, UBUNTU-CVE-2026-23072

## What is CVE-2026-23072?

CVE-2026-23072 is a medium-severity memory corruption vulnerability in Linux kernel, published on 4 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

l2tp: Fix memleak in l2tp_udp_encap_recv().

syzbot reported memleak of struct l2tp_session, l2tp_tunnel,
sock, etc. [0]

The cited commit moved down the validation of the protocol
version in l2tp_udp_encap_recv().

The new place requires an extra error handling to avoid the
memleak.

Let's call l2tp_session_put() there.

[0]:
BUG: memory leak
unreferenced object 0xffff88810a290200 (size 512):
  comm "syz.0.17", pid 6086, jiffies 4294944299
  hex dump (first 32 bytes):
    7d eb 04 0c 00 00 00 00 01 00 00 00 00 00 00 00  }...............
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc babb6a4f):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4958 [inline]
    slab_alloc_node mm/slub.c:5263 [inline]
    __do_kmalloc_node mm/slub.c:5656 [inline]
    __kmalloc_noprof+0x3e0/0x660 mm/slub.c:5669
    kmalloc_noprof include/linux/slab.h:961 [inline]
    kzalloc_noprof include/linux/slab.h:1094 [inline]
    l2tp_session_create+0x3a/0x3b0 net/l2tp/l2tp_core.c:1778
    pppol2tp_connect+0x48b/0x920 net/l2tp/l2tp_ppp.c:755
    __sys_connect_file+0x7a/0xb0 net/socket.c:2089
    __sys_connect+0xde/0x110 net/socket.c:2108
    __do_sys_connect net/socket.c:2114 [inline]
    __se_sys_connect net/socket.c:2111 [inline]
    __x64_sys_connect+0x1c/0x30 net/socket.c:2111
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2026-23072?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23072?

Apply the vendor's patch.

## Is CVE-2026-23072 being exploited?

There is no known exploitation of CVE-2026-23072 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23072 and fix it if it is affected.

What it is: CVE-2026-23072 is a medium-severity memory corruption vulnerability in Linux kernel, published on 4 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-23072 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-23072/ (Markdown: https://insights.sbomify.com/CVE-2026-23072/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23072
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23072
- OSV: https://osv.dev/vulnerability/CVE-2026-23072

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23072/
Summaries are generated and may contain mistakes; the official description above is the record.