# CVE-2026-89637: linux: In the Linux kernel, the following vulnerability has been resolved:  smb: client: fix UAF and buffer leak in cifs_che...

CVE-2026-89637 is fixed in 66 products on 1 platform, first by DEBIAN-CVE-2026-89637, released September 23, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-89637
- Priority: Urgent
- CVSS: 9.8 (critical)
- EPSS: 0.0060
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 11, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:  smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2  When a valid primary TRANSACT2 response has been received (mid->resp_buf set, mid->multiRsp true) and a subsequent secondary response causes cifs_check_trans2() to return false -- either because the SMB header is invalid (malformed != 0) or because check2ndT2() rejects the PDU -- handle_mid() overwrites mid->resp_buf with the new buffer (leaking the primary buffer) and, because mid->multiRsp is set, skips the server->smallbuf/bigbuf NULL-out.  When the user thread frees mid->resp_buf, server->smallbuf or server->bigbuf is left dangling; the demux thread reuses it for the next packet, resulting in a use-after-free.  Combine both early-exit conditions and, when mid->multiRsp is already set, abort the pending transaction inline: set multiEnd, call dequeue_mid() with malformed=true, and return true so handle_mid() exits without touching mid->resp_buf or the server buffer pointers.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | bpftool amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | bpftool-debuginfo amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | bpftool6.12 amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | bpftool6.12-debuginfo amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | bpftool6.18 amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | bpftool6.18-debuginfo amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | kernel amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | kernel-64kb sles 15.7 | 6.4.0-150700.53.90.1 | [SUSE-SU-2026:5091-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5091-1.md) | Nov 7, 2026 |
| Linux | kernel-azure sles 15.7 | 6.4.0-150700.53.90.1 | [SUSE-SU-2026:5091-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5091-1.md) | Nov 7, 2026 |
| Linux | kernel-debuginfo amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | kernel-debuginfo-common-aarch64 amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | kernel-debuginfo-common-x86_64 amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | kernel-default sles 15.7 | 6.4.0-150700.53.90.1 | [SUSE-SU-2026:5091-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5091-1.md) | Nov 7, 2026 |
| Linux | kernel-default-base sles 15.7 | 6.4.0-150700.53.90.1.150700.17.51.1 | [SUSE-SU-2026:5091-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5091-1.md) | Nov 7, 2026 |
| Linux | kernel-devel amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | kernel-docs sles 15.7 | 6.4.0-150700.53.90.1 | [SUSE-SU-2026:5091-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5091-1.md) | Nov 7, 2026 |
| Linux | kernel-headers amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | kernel-livepatch-6.1.188-233.393 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | kernel-livepatch-6.12.111-136.204 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | kernel-livepatch-6.18.51-120.162 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | kernel-livepatch-SLE15-SP7_Update_24 sles 15.7 | 1-150700.15.3.1 | [SUSE-SU-2026:5091-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5091-1.md) | Nov 7, 2026 |
| Linux | kernel-modules-extra amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | kernel-modules-extra-common amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | kernel-obs-build sles 15.7 | 6.4.0-150700.53.90.1 | [SUSE-SU-2026:5091-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5091-1.md) | Nov 7, 2026 |
| Linux | kernel-source sles 15.7 | 6.4.0-150700.53.90.1 | [SUSE-SU-2026:5091-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5091-1.md) | Nov 7, 2026 |
| Linux | kernel-syms sles 15.7 | 6.4.0-150700.53.90.1 | [SUSE-SU-2026:5091-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5091-1.md) | Nov 7, 2026 |
| Linux | kernel-tools amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | kernel-tools-debuginfo amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | kernel-tools-devel amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | kernel-zfcpdump sles 15.7 | 6.4.0-150700.53.90.1 | [SUSE-SU-2026:5091-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5091-1.md) | Nov 7, 2026 |
| Linux | kernel6.12 amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | kernel6.12-debuginfo amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | kernel6.12-debuginfo-common-aarch64 amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | kernel6.12-debuginfo-common-x86_64 amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | kernel6.12-devel amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | kernel6.12-headers amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | kernel6.12-modules-extra amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | kernel6.12-modules-extra-common amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | kernel6.12-tools amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | kernel6.12-tools-debuginfo amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | kernel6.12-tools-devel amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | kernel6.18 amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | kernel6.18-debuginfo amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | kernel6.18-debuginfo-common-aarch64 amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | kernel6.18-debuginfo-common-x86_64 amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | kernel6.18-devel amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | kernel6.18-headers amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | kernel6.18-modules-extra amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | kernel6.18-modules-extra-common amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | kernel6.18-tools amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | kernel6.18-tools-debuginfo amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | kernel6.18-tools-devel amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | linux Debian 14 | 7.2.6-1 | [DEBIAN-CVE-2026-89637](https://patchblox.com/security/data/fix/linux/debian-cve-2026-89637.md) | Sep 23, 2026 |
| Linux | microvm-kernel6.18 amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | perf amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | perf-debuginfo amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | perf6.12 amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | perf6.12-debuginfo amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | perf6.18 amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | perf6.18-debuginfo amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | python3-perf amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | python3-perf-debuginfo amzn 2023 | 1:6.1.188-233.393.amzn2023 | [ALAS2023-2026-3183](https://patchblox.com/security/data/fix/linux/alas2023-2026-3183.md) | Nov 7, 2026 |
| Linux | python3-perf6.12 amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | python3-perf6.12-debuginfo amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 |
| Linux | python3-perf6.18 amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |
| Linux | python3-perf6.18-debuginfo amzn 2023 | 1:6.18.51-120.162.amzn2023 | [ALAS2023-2026-3187](https://patchblox.com/security/data/fix/linux/alas2023-2026-3187.md) | Nov 7, 2026 |

---

Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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