Description
In the Linux kernel, the following vulnerability has been resolved:
l2tp: prevent possible tunnel refcount underflow
When a session is created, it sets a backpointer to its tunnel. When
the session refcount drops to 0, l2tp_session_free drops the tunnel
refcount if session->tunnel is non-NULL. However, session->tunnel is
set in l2tp_session_create, before the tunnel refcount is incremented
by l2tp_session_register, which leaves a small window where
session->tunnel is non-NULL when the tunnel refcount hasn't been
bumped.
Moving the assignment to l2tp_session_register is trivial but
l2tp_session_create calls l2tp_session_set_header_len which uses
session->tunnel to get the tunnel's encap. Add an encap arg to
l2tp_session_set_header_len to avoid using session->tunnel.
If l2tpv3 sessions have colliding IDs, it is possible for
l2tp_v3_session_get to race with l2tp_session_register and fetch a
session which doesn't yet have session->tunnel set. Add a check for
this case.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Linux | Linux | 3.2.99 – < 3.3, 3.16.54 – < 3.17, 4.4.225 – < 4.5, 4.9.225 – < 4.10, 4.14.182 – < 4.15, 4.15 | 3.3 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | linux | 6.11.4-1 | — |
| Debian 13 | linux | 6.11.4-1 | — |
| Debian 12 | linux | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Nvidia-BlueField 24.04 LTS | linux-bluefield | No fix yet | — |
| Ubuntu Nvidia-BlueField 22.04 LTS | linux-bluefield | No fix yet | — |
| Ubuntu 24.04 LTS | linux +20 | No fix yet | — |
| Ubuntu 24.04 LTS | linux-azure-6.11 | 6.11.0-1012.12~24.04.1 | — |
| Ubuntu 24.04 LTS | linux-gcp-6.11 | 6.11.0-1011.11~24.04.1 | — |
| Ubuntu 24.04 LTS | linux-nvidia-6.11 | 6.11.0-1007.7 | — |
| Ubuntu 24.04 LTS | linux-nvidia-tegra | 6.8.0-1035.38 | USN-8781-1 |
| Ubuntu 24.04 LTS | linux-oem-6.11 | 6.11.0-1015.15 | USN-7310-1 |
| Ubuntu 22.04 LTS | linux +59 | No fix yet | — |
| Ubuntu 20.04 LTS | linux-gke +28 | No fix yet | — |
Show 16 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | linux-gcp +14 | No fix yet | — |
| Ubuntu 16.04 LTS | linux-hwe-edge | No fix yet | — |
| Ubuntu Pro Realtime 24.04 LTS | linux-realtime +1 | No fix yet | — |
| Ubuntu Pro Realtime 22.04 LTS | linux-realtime +2 | No fix yet | — |
| Ubuntu Pro FIPS 20.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro FIPS 18.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro FIPS-updates 22.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro FIPS-updates 20.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro FIPS-updates 18.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro FIPS-updates 16.04 LTS | linux-fips | No fix yet | — |
| Ubuntu Pro FIPS-preview 22.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro 20.04 LTS | linux +21 | No fix yet | — |
| Ubuntu Pro 18.04 LTS | linux +12 | No fix yet | — |
| Ubuntu Pro 16.04 LTS | linux +7 | No fix yet | — |
| Ubuntu Pro 14.04 LTS | linux-aws +2 | No fix yet | — |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP6 | kernel-64kb +3 | 6.4.0-150600.23.47.2 | SUSE-SU-2025:1180-1 |
| SLES 15 SP6 | kernel-azure +1 | 6.4.0-150600.8.34.2 | SUSE-SU-2025:1177-1 |
| SLES 15 SP6 | kernel-coco +3 | 6.4.0-15061.21.coco15sp6.1 | SUSE-SU-2025:01919-1 |
| SLES 15 SP6 | kernel-default-base | 6.4.0-150600.23.47.2.150600.12.20.2 | SUSE-SU-2025:1180-1 |
| SLES 15 SP6 | kernel-docs +2 | 6.4.0-150600.23.47.1 | SUSE-SU-2025:1180-1 |
| SLES 15 SP6 | kernel-syms-azure | 6.4.0-150600.8.34.1 | SUSE-SU-2025:1177-1 |
| SLES 12 SP5 | kernel-syms +2 | 4.12.14-122.255.1 | SUSE-SU-2025:1293-1 |
Show 5 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLE Micro 6.1 | kernel-default-base | 6.4.0-28.1.21.6 | SUSE-SU-2025:20270-1 |
| SLE Micro 6.1 | kernel-livepatch-MICRO-6-0_Update_6 +1 | 1-3.1 | SUSE-SU-2025:20270-1, SUSE-SU-2025:20260-1 |
| SLE Micro 6.1 | kernel-rt +4 | 6.4.0-28.1 | SUSE-SU-2025:20270-1, SUSE-SU-2025:20260-1 |
| SLE Micro 6.0 | kernel-default-base | 6.4.0-28.1.21.6 | SUSE-SU-2025:20192-1 |
| SLE Micro 6.0 | kernel-livepatch-MICRO-6-0_Update_6 +1 | 1-3.1 | SUSE-SU-2025:20192-1, SUSE-SU-2025:20190-1 |
| SLE Micro 6.0 | kernel-rt +4 | 6.4.0-28.1 | SUSE-SU-2025:20192-1, SUSE-SU-2025:20190-1 |
| SLE Live Patching 15 SP6 | kernel-default | 6.4.0-150600.23.47.2 | SUSE-SU-2025:1180-1 |
| SLE Live Patching 15 SP6 | kernel-livepatch-SLE15-SP6-RT_Update_10 | 1-150600.1.5.1 | SUSE-SU-2025:1178-1 |
| SLE Live Patching 15 SP6 | kernel-livepatch-SLE15-SP6_Update_10 | 1-150600.13.5.1 | SUSE-SU-2025:1180-1 |
| SLE Live Patching 12 SP5 | kernel-default | 4.12.14-122.255.1 | SUSE-SU-2025:1293-1 |
| SLE Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_67 | 1-8.5.1 | SUSE-SU-2025:1293-1 |
| SUSE Real Time Module 15 SP6 | kernel-rt +3 | 6.4.0-150600.10.34.1 | SUSE-SU-2025:1178-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | kernel-source | 6.11.8-1.1 | openSUSE-SU-2024:14500-1 |
| openSUSE Tumbleweed | kernel-source-longterm | 6.12.11-1.1 | openSUSE-SU-2025:14705-1 |
| openSUSE Leap 15.6 | dtb-aarch64 +4 | 6.4.0-150600.23.47.1 | SUSE-SU-2025:1180-1 |
| openSUSE Leap 15.6 | kernel-64kb +5 | 6.4.0-150600.23.47.2 | SUSE-SU-2025:1180-1 |
| openSUSE Leap 15.6 | kernel-azure +1 | 6.4.0-150600.8.34.2 | SUSE-SU-2025:1177-1 |
| openSUSE Leap 15.6 | kernel-default-base | 6.4.0-150600.23.47.2.150600.12.20.2 | SUSE-SU-2025:1180-1 |
| openSUSE Leap 15.6 | kernel-rt +3 | 6.4.0-150600.10.34.1 | SUSE-SU-2025:1178-1 |
| openSUSE Leap 15.6 | kernel-syms-azure | 6.4.0-150600.8.34.1 | SUSE-SU-2025:1177-1 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | kernel | No fix yet | — |
| Azure Linux 2 (CBL-Mariner) | kernel | No fix yet | — |
Advisories 15
- WID-SEC-2024-3251 Linux Kernel: Mehrere Schwachstellen ermöglichen Denial of Service BSI CERT-Bund (WID) · Nov 11, 2026
- USN-8781-1 linux-nvidia-tegra vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-7310-1 linux-oem-6.11 vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- WID-SEC-2025-1439 Dell Secure Connect Gateway: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff BSI CERT-Bund (WID) · Oct 11, 2026
- SUSE-SU-2025:20270-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:20192-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:20260-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:20190-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:01919-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:1177-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:1180-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2025:14705-1 kernel-devel-longterm-6.12.11-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:1178-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:14500-1 kernel-devel-6.11.8-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:1293-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026