Description
In the Linux kernel, the following vulnerability has been resolved:
tcp: add accessors to read/set tp->snd_cwnd
We had various bugs over the years with code
breaking the assumption that tp->snd_cwnd is greater
than zero.
Lately, syzbot reported the WARN_ON_ONCE(!tp->prior_cwnd) added
in commit 8b8a321ff72c ("tcp: fix zero cwnd in tcp_cwnd_reduction")
can trigger, and without a repro we would have to spend
considerable time finding the bug.
Instead of complaining too late, we want to catch where
and when tp->snd_cwnd is set to an illegal value.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Linux | Linux | 2.6.17 | 5.15.47 |
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 | 5.18.5-1 | — |
| Debian 13 | linux | 5.18.5-1 | — |
| Debian 12 | linux | 5.18.5-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 24.04 LTS | linux-raspi-realtime | No fix yet | — |
| Ubuntu 22.04 LTS | linux +1 | 5.15.0-48.54 | — |
| Ubuntu 22.04 LTS | linux-aws | 5.15.0-1020.24 | — |
| Ubuntu 22.04 LTS | linux-azure | 5.15.0-1020.25 | — |
| Ubuntu 22.04 LTS | linux-azure-fde | 5.15.0-1024.30.1 | — |
| Ubuntu 22.04 LTS | linux-gcp | 5.15.0-1018.24 | — |
| Ubuntu 22.04 LTS | linux-gke | 5.15.0-1016.19 | — |
| Ubuntu 22.04 LTS | linux-gkeop | 5.15.0-1003.5 | — |
| Ubuntu 22.04 LTS | linux-ibm +1 | 5.15.0-1015.17 | — |
| Ubuntu 22.04 LTS | linux-intel-iotg | 5.15.0-1016.21 | — |
| Ubuntu 22.04 LTS | linux-kvm | 5.15.0-1018.22 | — |
| Ubuntu 22.04 LTS | linux-nvidia | 5.15.0-1007.7 | — |
| Ubuntu 22.04 LTS | linux-oracle | 5.15.0-1018.23 | — |
| Ubuntu 22.04 LTS | linux-riscv +32 | No fix yet | — |
| Ubuntu 20.04 LTS | linux-aws-5.15 | 5.15.0-1020.24~20.04.1 | — |
| Ubuntu 20.04 LTS | linux-azure-5.15 | 5.15.0-1020.25~20.04.1 | — |
| Ubuntu 20.04 LTS | linux-gcp-5.15 | 5.15.0-1018.24~20.04.1 | — |
| Ubuntu 20.04 LTS | linux-gke +28 | No fix yet | — |
| Ubuntu 20.04 LTS | linux-hwe-5.15 +1 | 5.15.0-48.54~20.04.1 | — |
| Ubuntu 20.04 LTS | linux-intel-iotg-5.15 | 5.15.0-1016.21~20.04.1 | — |
| Ubuntu 20.04 LTS | linux-oracle-5.15 | 5.15.0-1018.23~20.04.1 | — |
| Ubuntu 20.04 LTS | linux-riscv-5.15 | 5.15.0-1019.22~20.04.1 | — |
| Ubuntu 18.04 LTS | linux-gcp +14 | No fix yet | — |
| Ubuntu 16.04 LTS | linux-hwe-edge | No fix yet | — |
Show 11 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro Realtime 22.04 LTS | linux-realtime | 5.15.0-1021.21 | — |
| 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 16.04 LTS | linux-fips | 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 20.04 LTS | linux +10 | 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 +3 | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 9 | perf +29 | 5.14.0-162.6.1.el9_1 | RHSA-2022:8267 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP5 | kernel-64kb +6 | 5.14.21-150500.55.100.1 | SUSE-SU-2025:1241-1 |
| SLES 15 SP5 | kernel-default-base | 5.14.21-150500.55.100.1.150500.6.47.1 | SUSE-SU-2025:1241-1 |
| SLES 12 SP5 | kernel-syms +2 | 4.12.14-122.258.1 | SUSE-SU-2025:01600-1 |
Show 5 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 15 SP5 | kernel-default-base | 5.14.21-150500.55.100.1.150500.6.47.1 | SUSE-SU-2025:1241-1 |
| SLES for SAP 15 SP5 | kernel-docs +4 | 5.14.21-150500.55.100.1 | SUSE-SU-2025:1241-1 |
| SLE Micro 5.5 | kernel-default-base | 5.14.21-150500.55.100.1.150500.6.47.1 | SUSE-SU-2025:1241-1 |
| SLE Micro 5.5 | kernel-rt +1 | 5.14.21-150500.13.91.1 | SUSE-SU-2025:1176-1 |
| SLE Micro 5.5 | kernel-source +1 | 5.14.21-150500.55.100.1 | SUSE-SU-2025:1241-1 |
| SLE Live Patching 15 SP5 | kernel-default | 5.14.21-150500.55.100.1 | SUSE-SU-2025:1241-1 |
| SLE Live Patching 15 SP5 | kernel-livepatch-SLE15-SP5_Update_25 | 1-150500.11.3.1 | SUSE-SU-2025:1241-1 |
| SLE Live Patching 12 SP5 | kernel-default | 4.12.14-122.258.1 | SUSE-SU-2025:01600-1 |
| SLE Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_68 | 1-8.3.1 | SUSE-SU-2025:01600-1 |
| SLE HPC 15 SP5 | kernel-64kb +5 | 5.14.21-150500.55.100.1 | SUSE-SU-2025:1241-1 |
| SLE HPC 15 SP5 | kernel-default-base | 5.14.21-150500.55.100.1.150500.6.47.1 | SUSE-SU-2025:1241-1 |
Advisories 5
- WID-SEC-2025-2107 Linux Kernel: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 9, 2026
- RHSA-2022:8267 Red Hat Security Advisory: kernel security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Oct 17, 2026
- SUSE-SU-2025:1176-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:1241-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:01600-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026