In the Linux kernel, the following vulnerability has been resolved:
cifs: fix DFS traversal oops without CONFIG_CIFS_DFS_UPCALL
When compiled with CONFIG_CIFS_DFS_UPCALL disabled, cifs_dfs_d_automount is NULL. cifs.ko logic for mapping CIFS_FATTR_DFS_REFERRAL attributes to S_AUTOMOUNT and corresponding dentry flags is retained regardless of CONFIG_CIFS_DFS_UPCALL, leading to a NULL pointer dereference in VFS follow_automount() when traversing a DFS referral link: BUG: kernel NULL pointer dereference, address: 0000000000000000 ... Call Trace: <TASK> __traverse_mounts+0xb5/0x220 ? cifs_revalidate_mapping+0x65/0xc0 [cifs] step_into+0x195/0x610 ? lookup_fast+0xe2/0xf0 path_lookupat+0x64/0x140 filename_lookup+0xc2/0x140 ? __create_object+0x299/0x380 ? kmem_cache_alloc+0x119/0x220 ? user_path_at_empty+0x31/0x50 user_path_at_empty+0x31/0x50 __x64_sys_chdir+0x2a/0xd0 ? exit_to_user_mode_prepare+0xca/0x100 do_syscall_64+0x42/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc
This fix adds an inline cifs_dfs_d_automount() {return -EREMOTE} handler when CONFIG_CIFS_DFS_UPCALL is disabled. An alternative would be to avoid flagging S_AUTOMOUNT, etc. without CONFIG_CIFS_DFS_UPCALL. This approach was chosen as it provides more control over the error path.
CVSS Details
- CVSS 3.1 Base Score: 5.5
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon Linux Ami 2 | — | Upgrade kernel-develUpgrade kernel-toolsUpgrade kernel-tools-develUpgrade kernelUpgrade kernel-debuginfo-common-x86_64Upgrade kernel-livepatch-5.15.106-64.140Upgrade kernel-debuginfo-common-aarch64Upgrade python-perfUpgrade bpftoolUpgrade kernel-livepatch-4.14.313-235.533Upgrade kernel-livepatch-5.10.177-158.645Upgrade kernel-debuginfoUpgrade python-perf-debuginfoUpgrade bpftool-debuginfoUpgrade kernel-headersUpgrade kernel-tools-debuginfoUpgrade perf-debuginfoUpgrade perf | May 20, 2026 | May 20, 2026 |
| Amazon_linux_2023 | — | Upgrade kernel-debuginfo-common-x86_64Upgrade python3-perf-debuginfoUpgrade kernel-libbpfUpgrade kernel-toolsUpgrade kernel-headersUpgrade bpftool-debuginfoUpgrade kernel-tools-debuginfoUpgrade kernel-debuginfoUpgrade bpftoolUpgrade kernel-livepatch-6.1.23-36.46Upgrade kernel-libbpf-develUpgrade kernel-tools-develUpgrade kernel-develUpgrade perfUpgrade kernelUpgrade kernel-libbpf-staticUpgrade python3-perfUpgrade kernel-debuginfo-common-aarch64Upgrade perf-debuginfo | Oct 16, 2025 | Sep 15, 2025 |
| Debian | — | Upgrade linux | Sep 17, 2025 | Sep 17, 2025 |
| Huawei Euleros 2_0_sp13 | — | Upgrade python3-perfUpgrade kernelUpgrade kernel-toolsUpgrade kernel-abi-stablelistsUpgrade kernel-tools-libsUpgrade bpftool | Mar 10, 2026 | Mar 10, 2026 |
| Redhat_linux | — | No solution exists | Jul 17, 2026 | Sep 15, 2025 |
| Ubuntu | — | Upgrade linux-oracleUpgrade linux-kvmUpgrade linux-azure-5.15Upgrade linux-azure-fipsUpgrade linux-ibm-5.15Upgrade linux-gkeUpgrade linux-oracle-5.4Upgrade linux-nvidia-tegraUpgrade linux-lowlatencyUpgrade linux-riscv-5.15Upgrade linux-gcpUpgrade linux-aws-5.15Upgrade linux-nvidiaUpgrade linux-intel-iot-realtimeUpgrade linux-gkeopUpgrade linux-fipsUpgrade linux-azure-fde-5.15Upgrade linux-oracle-5.15Upgrade linux-aws-5.4Upgrade linux-nvidia-tegra-5.15Upgrade linux-ibm-5.4Upgrade linux-intel-iotgUpgrade linux-xilinx-zynqmpUpgrade linux-lowlatency-hwe-5.15Upgrade linux-raspiUpgrade linux-raspi-5.4Upgrade linuxUpgrade linux-gcp-fipsUpgrade linux-gcp-5.4Upgrade linux-gcp-5.15Upgrade linux-ibmUpgrade linux-bluefieldUpgrade linux-intel-iotg-5.15Upgrade linux-azureUpgrade linux-hwe-5.4Upgrade linux-iotUpgrade linux-azure-5.4Upgrade linux-aws-fipsUpgrade linux-nvidia-tegra-igxUpgrade linux-realtimeUpgrade linux-hwe-5.15Upgrade linux-aws | Sep 19, 2025 | Sep 16, 2025 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Oct 15, 2025 | Sep 15, 2025 |
Prioritise with Active Threat Intelligence
With curated Threat Intelligence, you can see which vulnerabilities truly put you at risk, prioritize what matters most, and act before attackers do.
Explore Intelligence Hub