Description
In the Linux kernel, the following vulnerability has been resolved:
tcp: Correct signedness in skb remaining space calculation
Syzkaller reported a bug [1] where sk->sk_forward_alloc can overflow.
When we send data, if an skb exists at the tail of the write queue, the
kernel will attempt to append the new data to that skb. However, the code
that checks for available space in the skb is flawed:
'''
copy = size_goal - skb->len
'''
The types of the variables involved are:
'''
copy: ssize_t (s64 on 64-bit systems)
size_goal: int
skb->len: unsigned int
'''
Due to C's type promotion rules, the signed size_goal is converted to an
unsigned int to match skb->len before the subtraction. The result is an
unsigned int.
When this unsigned int result is then assigned to the s64 copy variable,
it is zero-extended, preserving its non-negative value. Consequently, copy
is always >= 0.
Assume we are sending 2GB of data and size_goal has been adjusted to a
value smaller than skb->len. The subtraction will result in copy holding a
very large positive integer. In the subsequent logic, this large value is
used to update sk->sk_forward_alloc, which can easily cause it to overflow.
The syzkaller reproducer uses TCP_REPAIR to reliably create this
condition. However, this can also occur in real-world scenarios. The
tcp_bound_to_half_wnd() function can also reduce size_goal to a small
value. This would cause the subsequent tcp_wmem_schedule() to set
sk->sk_forward_alloc to a value close to INT_MAX. Further memory
allocation requests would then cause sk_forward_alloc to wrap around and
become negative.
[1]: https://syzkaller.appspot.com/bug?extid=de6565462ab540f50e47
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Linux | Linux | 6.5 | 6.6.99 |
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 | 6.16.3-1 | — |
| Debian 13 | linux | 6.12.41-1 | DSA-5975-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Nvidia-BlueField 24.04 LTS | linux-bluefield | 6.8.0-1016.20 | — |
| Ubuntu 25.10 | linux-azure-fde | No fix yet | — |
| Ubuntu 24.04 LTS | linux | 6.8.0-100.100 | USN-8028-1 |
| Ubuntu 24.04 LTS | linux-aws +1 | 6.8.0-1046.49 | USN-8028-5 |
| Ubuntu 24.04 LTS | linux-aws-6.14 +2 | 6.14.0-1017.17~24.04.1 | USN-7934-1, USN-7879-3 |
| Ubuntu 24.04 LTS | linux-azure | 6.8.0-1046.52 | USN-8074-1 |
| Ubuntu 24.04 LTS | linux-azure-fde | 6.8.0-1046.53 | — |
| Ubuntu 24.04 LTS | linux-azure-nvidia | 6.8.0-1039.42 | — |
| Ubuntu 24.04 LTS | linux-gcp | 6.8.0-1047.50 | USN-8031-3 |
| Ubuntu 24.04 LTS | linux-gcp-6.14 | 6.14.0-1020.21~24.04.1 | USN-7879-4 |
| Ubuntu 24.04 LTS | linux-gke | 6.8.0-1043.48 | USN-8031-3 |
| Ubuntu 24.04 LTS | linux-gkeop | 6.8.0-1030.33 | USN-8028-5 |
| Ubuntu 24.04 LTS | linux-hwe-6.14 | 6.14.0-36.36~24.04.1 | USN-7879-1 |
| Ubuntu 24.04 LTS | linux-ibm | 6.8.0-1044.44 | USN-8028-8 |
| Ubuntu 24.04 LTS | linux-intel +12 | No fix yet | — |
| Ubuntu 24.04 LTS | linux-lowlatency | 6.8.0-100.100.1 | USN-8052-1 |
| Ubuntu 24.04 LTS | linux-nvidia-lowlatency | 6.8.0-1046.49.1 | USN-8028-7 |
| Ubuntu 24.04 LTS | linux-nvidia-tegra | 6.8.0-1020.20 | — |
| Ubuntu 24.04 LTS | linux-oem-6.14 | 6.14.0-1016.16 | USN-7880-1 |
| Ubuntu 24.04 LTS | linux-oracle | 6.8.0-1043.44 | USN-8028-5 |
| Ubuntu 24.04 LTS | linux-raspi | 6.8.0-1047.51 | USN-8028-1 |
| Ubuntu 24.04 LTS | linux-riscv-6.14 | 6.14.0-36.36.1~24.04.1 | — |
| Ubuntu 24.04 LTS | linux-xilinx | 6.8.0-1023.24 | USN-8052-2 |
| Ubuntu 22.04 LTS | linux-aws-6.8 +1 | 6.8.0-1046.49~22.04.1 | USN-8028-5 |
| Ubuntu 22.04 LTS | linux-azure-6.8 | 6.8.0-1051.57~22.04.1 | USN-8126-1 |
| Ubuntu 22.04 LTS | linux-azure-fde-6.8 | 6.8.0-1046.53~22.04.1 | — |
| Ubuntu 22.04 LTS | linux-gcp-6.8 | 6.8.0-1047.50~22.04.2 | USN-8031-1 |
| Ubuntu 22.04 LTS | linux-hwe-6.8 +1 | 6.8.0-100.100~22.04.1 | USN-8028-6 |
| Ubuntu 22.04 LTS | linux-ibm-6.8 | 6.8.0-1044.44~22.04.1 | USN-8028-8 |
| Ubuntu 22.04 LTS | linux-lowlatency-hwe-6.8 | 6.8.0-100.100.1~22.04.1 | USN-8028-6 |
| Ubuntu 22.04 LTS | linux-oracle-6.8 | 6.8.0-1043.44~22.04.1 | USN-8028-5 |
| Ubuntu 22.04 LTS | linux-riscv +32 | No fix yet | — |
| Ubuntu 20.04 LTS | linux-gke +28 | No fix yet | — |
Show 5 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-raspi-realtime | 6.8.0-2037.38 | USN-8028-3 |
| Ubuntu Pro Realtime 24.04 LTS | linux-realtime | 6.8.1-1041.42 | USN-8028-3 |
| Ubuntu Pro Realtime 24.04 LTS | linux-realtime-6.14 | 6.14.0-1016.16~24.04.1 | USN-7879-2 |
| Ubuntu Pro Realtime 22.04 LTS | linux-realtime-6.8 | 6.8.1-1041.42~22.04.1 | USN-8028-2 |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-aws-fips | 6.8.0-1046.49+fips1 | USN-8028-4 |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-azure-fips | 6.8.0-1046.52+fips1 | USN-8074-2 |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-fips | 6.8.0-100.100+fips1 | USN-8028-4 |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-gcp-fips | 6.8.0-1047.50+fips1 | USN-8031-2 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 10 | rv +77 | 6.12.0-55.33.1.el10_0 | RHSA-2025:15782 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 10 | kernel-doc +1 | 6.12.0-55.33.1.el10_0 | ALSA-2025:15782 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | kernel-64kb +5 | 6.4.0-150700.53.11.1 | SUSE-SU-2025:02997-1 |
| SLES 15 SP7 | kernel-azure +2 | 6.4.0-150700.20.11.1 | SUSE-SU-2025:03011-1 |
| SLES 15 SP7 | kernel-default-base | 6.4.0-150700.53.11.1.150700.17.9.4 | SUSE-SU-2025:02997-1 |
| SLES 15 SP7 | kernel-docs | 6.4.0-150700.53.11.3 | SUSE-SU-2025:02997-1 |
| SLES 15 SP6 | kernel-64kb +6 | 6.4.0-150600.23.65.1 | SUSE-SU-2025:02996-1 |
| SLES 15 SP6 | kernel-azure +2 | 6.4.0-150600.8.48.1 | SUSE-SU-2025:02969-1 |
| SLES 15 SP6 | kernel-coco +3 | 6.4.0-15061.28.coco15sp6.1 | SUSE-SU-2025:02923-1 |
| SLES 15 SP6 | kernel-default-base | 6.4.0-150600.23.65.1.150600.12.28.4 | SUSE-SU-2025:02996-1 |
Show 9 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | kernel-64kb +7 | 6.12.0-160000.6.1 | SUSE-SU-2025:21139-1 |
| SLES for SAP 16.0 | kernel-default-base | 6.12.0-160000.6.1.160000.2.4 | SUSE-SU-2025:21139-1 |
| SLES 16.0 | kernel-64kb +7 | 6.12.0-160000.6.1 | SUSE-SU-2025:21179-1, SUSE-SU-2025:21139-1 |
| SLES 16.0 | kernel-default-base | 6.12.0-160000.6.1.160000.2.4 | SUSE-SU-2025:21139-1 |
| SLE Micro 6.2 | kernel-default-base | 6.12.0-160000.6.1.160000.2.4 | SUSE-SU-2025:21074-1 |
| SLE Micro 6.2 | kernel-rt +5 | 6.12.0-160000.6.1 | SUSE-SU-2026:20560-1, SUSE-SU-2025:21074-1 |
| SLE Micro 6.1 | kernel-default-base | 6.4.0-32.1.21.10 | SUSE-SU-2025:20602-1 |
| SLE Micro 6.1 | kernel-rt +1 | 6.4.0-35.1 | SUSE-SU-2025:20601-1 |
| SLE Micro 6.1 | kernel-source +2 | 6.4.0-32.1 | SUSE-SU-2025:20602-1 |
| SLE Micro 6.0 | kernel-default-base | 6.4.0-32.1.21.10 | SUSE-SU-2025:20586-1 |
| SLE Micro 6.0 | kernel-rt +1 | 6.4.0-35.1 | SUSE-SU-2025:20577-1 |
| SLE Micro 6.0 | kernel-source +2 | 6.4.0-32.1 | SUSE-SU-2025:20586-1 |
| SLE Live Patching 15 SP7 | kernel-default | 6.4.0-150700.53.11.1 | SUSE-SU-2025:02997-1 |
| SLE Live Patching 15 SP7 | kernel-livepatch-SLE15-SP7-RT_Update_3 | 1-150700.1.5.1 | SUSE-SU-2025:02853-1 |
| SLE Live Patching 15 SP7 | kernel-livepatch-SLE15-SP7_Update_3 | 1-150700.15.3.4 | SUSE-SU-2025:02997-1 |
| SLE Live Patching 15 SP6 | kernel-default | 6.4.0-150600.23.65.1 | SUSE-SU-2025:02996-1 |
| SLE Live Patching 15 SP6 | kernel-livepatch-SLE15-SP6-RT_Update_14 | 1-150600.1.5.1 | SUSE-SU-2025:03023-1 |
| SLE Live Patching 15 SP6 | kernel-livepatch-SLE15-SP6_Update_14 | 1-150600.13.3.4 | SUSE-SU-2025:02996-1 |
| SUSE Real Time Module 15 SP7 | kernel-rt +2 | 6.4.0-150700.7.13.1 | SUSE-SU-2025:02853-1 |
| SUSE Real Time Module 15 SP6 | kernel-rt +3 | 6.4.0-150600.10.49.1 | SUSE-SU-2025:03023-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 16.0 | kernel-default-base | 6.12.0-160000.6.1.160000.2.4 | openSUSE-SU-2025:20081-1 |
| openSUSE Leap 16.0 | kernel-rt +10 | 6.12.0-160000.6.1 | openSUSE-SU-2025:20081-1 |
| openSUSE Leap 15.6 | dtb-aarch64 +10 | 6.4.0-150600.23.65.1 | SUSE-SU-2025:02996-1 |
| openSUSE Leap 15.6 | kernel-azure +2 | 6.4.0-150600.8.48.1 | SUSE-SU-2025:02969-1 |
| openSUSE Leap 15.6 | kernel-default-base | 6.4.0-150600.23.65.1.150600.12.28.4 | SUSE-SU-2025:02996-1 |
| openSUSE Leap 15.6 | kernel-rt +3 | 6.4.0-150600.10.49.1 | SUSE-SU-2025:03023-1 |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | kernel-livepatch-6.12.40-63.114 | 1:1.0-0.amzn2023 | ALAS2023-2025-1145 |
| Amazon Linux 2023 | perf6.12 +14 | 1:6.12.40-63.114.amzn2023 | ALAS2023-2025-1145 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | kernel | 6.6.104.2-1 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 10 | rv +28 | 6.12.0-55.33.1.0.1.el10_0 | ELSA-2025-15782 |
| Oracle Linux 9 | kernel-uek +34 | 6.12.0-103.40.4.1.el10uek | ELSA-2025-20551 |
Advisories 45
- WID-SEC-2025-1653 Linux Kernel: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 12, 2026
- USN-8028-5 linux-aws, linux-aws-6.8, linux-gkeop, linux-nvidia, linux-nvidia-6.8, linux-oracle, linux-oracle-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8126-1 linux-azure-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8028-8 linux-ibm, linux-ibm-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8028-6 linux-hwe-6.8, linux-lowlatency-hwe-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8052-1 linux-lowlatency vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8052-2 linux-xilinx vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8074-1 linux-azure vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8074-2 linux-azure-fips vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8031-3 linux-gcp, linux-gke vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8028-1 linux, linux-raspi vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8028-4 linux-aws-fips, linux-fips vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8028-3 linux-realtime, linux-raspi-realtime vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8028-2 linux-realtime-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8028-7 linux-nvidia-lowlatency vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8031-2 linux-gcp-fips vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-8031-1 linux-gcp-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-7934-1 linux-azure, linux-azure-6.14 vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-7879-4 linux-gcp-6.14, linux-raspi vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-7879-3 linux-aws-6.14, linux-oracle-6.14 vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-7880-1 linux-oem-6.14 vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- USN-7879-2 linux-realtime-6.14 vulnerabilities Ubuntu Security Notices (USN) · Nov 3, 2026
- ALSA-2025:15782 Moderate: kernel security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2025:15782 Red Hat Security Advisory: kernel security update Red Hat Security Advisories (RHSA) · Oct 16, 2026
- SUSE-SU-2026:20560-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Jul 9, 2026
- USN-7879-1 linux, linux-aws, linux-gcp, linux-hwe-6.14, linux-oracle, linux-realtime vulnerabilities Ubuntu Security Notices (USN) · Jun 3, 2026
- openSUSE-SU-2025:20081-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:21179-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:21139-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:21074-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:20601-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:20602-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:02997-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:20586-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:20577-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:03011-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:02996-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Mar 23, 2026
- DSA-5975-1 linux - security update Debian Security (DSA / DLA) · Mar 9, 2026
- SUSE-SU-2025:02853-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:02923-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:02969-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:03023-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026
- ALAS2023-2025-1145 Important: kernel6.12 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Oct 2, 2025
- ELSA-2025-15782 Moderate: kernel security update (Oracle Linux 10) Oracle Linux Security Advisories (ELSA) · Sep 18, 2025
- ELSA-2025-20551 Important: Unbreakable Enterprise kernel security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Sep 8, 2025