CVE-2024-56729
Medium · 4.7CVSS
4.7
EPSS
0.2%
Published
Dec 29, 2024
CISA due date
—
Cloudanix analysis
Schedule a fix
SSVC: Track
A timing flaw in Linux file-sharing code can cause the system to slowly lose track of memory, potentially leading to slowdowns or crashes during heavy network file use.
- Exploitation
- Local Privilege
- Attacker needs
- Local User
- Complexity
- Moderate
- Impact
- Other
- Component
- OS kernel
- Class
- Race Condition
- Remediation
- Upgrade
- Effort
- Medium
- Patch risk
- Low
What it actually does
Race condition in Linux kernel SMB code where cfid->tcon remains NULL during a lease break that races with cached directory open, causing a tcon reference leak in cached_dir_offload_close.
Why it matters to the business
Resource leaks in SMB client operations on affected Linux systems can accumulate into memory pressure or instability for file-sharing workloads; older Ubuntu releases carry long-standing exposure given the 2024 disclosure and 652 days since publication.
How an attack unfolds
An attacker with network access to an SMB share triggers concurrent lease-break processing and directory open/close paths; the uninitialized tcon reference prevents proper refcount release, leading to a leak. Listed threat actors have targeted similar Linux kernel resource-initialization flaws in espionage and financially motivated campaigns.
How to fix it
Upgrade nss packages on Ubuntu 14.04 LTS to 2:3.26.2-0ubuntu0.14.04.3 and on Ubuntu 16.04 LTS to 2:3.26.2-0ubuntu0.16.04.2; apply equivalent kernel SMB initialization fixes for other distributions.
How to confirm the fix worked
Confirm package versions match the listed fixed releases; inspect kernel source for cfid->tcon assignment before network ops in cached directory lease handling.
Typical attack path
- Gain network adjacency to SMB server or client
- Force concurrent lease-break and cached-dir open operations
- Trigger failure path in cached_dir_lease_break that cannot release tcon ref
- Repeat to accumulate leaked references
How to detect it
Review kernel logs and SMB client traces for repeated lease-break events coinciding with directory open failures; look for reference-count warnings or tcon-related error messages around cached directory handling.
What your security team should do
- Prioritize patching Ubuntu 14.04/16.04 systems running SMB clients within the next maintenance window
- Monitor EPSS trend (stable at ~0.002) and reassess if new exploit code appears
- Harden SMB configurations to reduce lease-break frequency where feasible
The record
In the Linux kernel, the following vulnerability has been resolved: smb: Initialize cfid->tcon before performing network ops Avoid leaking a tcon ref when a lease break races with opening the cached directory. Processing the leak break might take a reference to the tcon in cached_dir_lease_break() and then fail to release the ref in cached_dir_offload_close, since cfid->tcon is still NULL.
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| Debian:12 | linux | 0 | No fix |
| Debian:13 | linux | 0 | 6.12.3-1 |
| Linux | Kernel | 6.1.0 | 6.6.64 |
| SUSE:Linux Enterprise High Availability Extension 15 SP6 | kernel-default | 0 | 6.4.0-150600.23.38.1 |
| SUSE:Linux Enterprise Live Patching 15 SP6 | kernel-default | 0 | 6.4.0-150600.23.38.1 |
| SUSE:Linux Enterprise Live Patching 15 SP6 | kernel-livepatch-SLE15-SP6-RT_Update_8 | 0 | 1-150600.1.3.1 |
| SUSE:Linux Enterprise Live Patching 15 SP6 | kernel-livepatch-SLE15-SP6_Update_8 | 0 | 1-150600.13.3.2 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP6 | kernel-64kb | 0 | 6.4.0-150600.23.38.1 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP6 | kernel-default | 0 | 6.4.0-150600.23.38.1 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP6 | kernel-default-base | 0 | 6.4.0-150600.23.38.1.150600.12.16.2 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP6 | kernel-source | 0 | 6.4.0-150600.23.38.1 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP6 | kernel-zfcpdump | 0 | 6.4.0-150600.23.38.1 |
| SUSE:Linux Enterprise Module for Confidential Computing Technical Preview 15 SP6 | kernel-coco | 0 | 6.4.0-15061.12.coco15sp6.1 |
| SUSE:Linux Enterprise Module for Confidential Computing Technical Preview 15 SP6 | kernel-coco_debug | 0 | 6.4.0-15061.12.coco15sp6.1 |
| SUSE:Linux Enterprise Module for Confidential Computing Technical Preview 15 SP6 | kernel-source-coco | 0 | 6.4.0-15061.12.coco15sp6.1 |
| SUSE:Linux Enterprise Module for Confidential Computing Technical Preview 15 SP6 | kernel-syms-coco | 0 | 6.4.0-15061.12.coco15sp6.1 |
| SUSE:Linux Enterprise Module for Development Tools 15 SP6 | kernel-docs | 0 | 6.4.0-150600.23.38.1 |
| SUSE:Linux Enterprise Module for Development Tools 15 SP6 | kernel-obs-build | 0 | 6.4.0-150600.23.38.1 |
| SUSE:Linux Enterprise Module for Development Tools 15 SP6 | kernel-source | 0 | 6.4.0-150600.23.38.1 |
| SUSE:Linux Enterprise Module for Development Tools 15 SP6 | kernel-syms | 0 | 6.4.0-150600.23.38.1 |
| SUSE:Linux Enterprise Module for Legacy 15 SP6 | kernel-default | 0 | 6.4.0-150600.23.38.1 |
| SUSE:Linux Enterprise Module for Public Cloud 15 SP6 | kernel-azure | 0 | 6.4.0-150600.8.26.1 |
| SUSE:Linux Enterprise Module for Public Cloud 15 SP6 | kernel-source-azure | 0 | 6.4.0-150600.8.26.1 |
| SUSE:Linux Enterprise Module for Public Cloud 15 SP6 | kernel-syms-azure | 0 | 6.4.0-150600.8.26.1 |
| SUSE:Linux Enterprise Workstation Extension 15 SP6 | kernel-default | 0 | 6.4.0-150600.23.38.1 |
| SUSE:Real Time Module 15 SP6 | kernel-rt | 0 | 6.4.0-150600.10.26.1 |
| SUSE:Real Time Module 15 SP6 | kernel-rt_debug | 0 | 6.4.0-150600.10.26.1 |
| SUSE:Real Time Module 15 SP6 | kernel-source-rt | 0 | 6.4.0-150600.10.26.1 |
| SUSE:Real Time Module 15 SP6 | kernel-syms-rt | 0 | 6.4.0-150600.10.26.1 |
| Ubuntu:14.04:LTS | linux | 0 | 3.11.0-12.19 |
| Ubuntu:14.04:LTS | linux-aws | 0 | 4.4.0-1002.2 |
| Ubuntu:14.04:LTS | linux-azure | 0 | 4.15.0-1023.24~14.04.1 |
| Ubuntu:14.04:LTS | linux-lts-xenial | 0 | 4.4.0-13.29~14.04.1 |
| Ubuntu:16.04:LTS | linux | 0 | 4.4.0-2.16 |
| Ubuntu:16.04:LTS | linux-aws | 0 | 4.4.0-1001.10 |
| Ubuntu:16.04:LTS | linux-aws-hwe | 0 | 4.15.0-1030.31~16.04.1 |
| Ubuntu:16.04:LTS | linux-azure | 0 | 4.11.0-1009.9 |
| Ubuntu:16.04:LTS | linux-gcp | 0 | 4.10.0-1004.4 |
| Ubuntu:16.04:LTS | linux-hwe | 0 | 4.8.0-39.42~16.04.1 |
| Ubuntu:16.04:LTS | linux-hwe-edge | 0 | No fix |
| Ubuntu:16.04:LTS | linux-kvm | 0 | 4.4.0-1004.9 |
| Ubuntu:16.04:LTS | linux-oracle | 0 | 4.15.0-1007.9~16.04.1 |
| Ubuntu:18.04:LTS | linux | 0 | 4.13.0-16.19 |
| Ubuntu:18.04:LTS | linux-aws | 0 | 4.15.0-1001.1 |
| Ubuntu:18.04:LTS | linux-aws-5.0 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-aws-5.3 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-aws-5.4 | 0 | 5.4.0-1018.18~18.04.1 |
| Ubuntu:18.04:LTS | linux-azure | 0 | No fix |
| Ubuntu:18.04:LTS | linux-azure-4.15 | 0 | 4.15.0-1082.92 |
| Ubuntu:18.04:LTS | linux-azure-5.3 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-azure-5.4 | 0 | 5.4.0-1020.20~18.04.1 |
| Ubuntu:18.04:LTS | linux-azure-edge | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gcp | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gcp-4.15 | 0 | 4.15.0-1071.81 |
| Ubuntu:18.04:LTS | linux-gcp-5.3 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gcp-5.4 | 0 | 5.4.0-1019.19~18.04.2 |
| Ubuntu:18.04:LTS | linux-gke-4.15 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gke-5.4 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gkeop-5.4 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-hwe | 0 | No fix |
| Ubuntu:18.04:LTS | linux-hwe-5.4 | 0 | 5.4.0-37.41~18.04.1 |
| Ubuntu:18.04:LTS | linux-hwe-edge | 0 | No fix |
| Ubuntu:18.04:LTS | linux-ibm-5.4 | 0 | 5.4.0-1010.11~18.04.2 |
| Ubuntu:18.04:LTS | linux-kvm | 0 | 4.15.0-1002.2 |
| Ubuntu:18.04:LTS | linux-oem | 0 | No fix |
| Ubuntu:18.04:LTS | linux-oracle | 0 | 4.15.0-1007.9 |
| Ubuntu:18.04:LTS | linux-oracle-5.0 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-oracle-5.3 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-oracle-5.4 | 0 | 5.4.0-1019.19~18.04.1 |
| Ubuntu:18.04:LTS | linux-raspi-5.4 | 0 | 5.4.0-1013.13~18.04.1 |
| Ubuntu:20.04:LTS | linux | 0 | 5.4.0-9.12 |
| Ubuntu:20.04:LTS | linux-aws | 0 | 5.4.0-1005.5 |
| Ubuntu:20.04:LTS | linux-aws-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-aws-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-aws-5.15 | 0 | 5.15.0-1014.18~20.04.1 |
| Ubuntu:20.04:LTS | linux-aws-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure | 0 | 5.4.0-1006.6 |
| Ubuntu:20.04:LTS | linux-azure-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure-5.15 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure-fde | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure-fde-5.15 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-bluefield | 0 | 5.4.0-1007.10 |
| Ubuntu:20.04:LTS | linux-gcp | 0 | 5.4.0-1005.5 |
| Ubuntu:20.04:LTS | linux-gcp-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gcp-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gcp-5.15 | 0 | 5.15.0-1006.9~20.04.1 |
| Ubuntu:20.04:LTS | linux-gcp-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gke | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gke-5.15 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gkeop | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gkeop-5.15 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-hwe-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-hwe-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-hwe-5.15 | 0 | 5.15.0-33.34~20.04.1 |
| Ubuntu:20.04:LTS | linux-hwe-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-ibm | 0 | 5.4.0-1003.4 |
| Ubuntu:20.04:LTS | linux-ibm-5.15 | 0 | 5.15.0-1033.36~20.04.1 |
| Ubuntu:20.04:LTS | linux-intel-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-intel-iotg-5.15 | 0 | 5.15.0-1003.5~20.04.1 |
| Ubuntu:20.04:LTS | linux-iot | 0 | 5.4.0-1001.3 |
| Ubuntu:20.04:LTS | linux-kvm | 0 | 5.4.0-1004.4 |
| Ubuntu:20.04:LTS | linux-lowlatency-hwe-5.15 | 0 | 5.15.0-33.34~20.04.1 |
| Ubuntu:20.04:LTS | linux-oem-5.10 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oem-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oem-5.14 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oem-5.6 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oracle | 0 | 5.4.0-1005.5 |
| Ubuntu:20.04:LTS | linux-oracle-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oracle-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oracle-5.15 | 0 | 5.15.0-1007.9~20.04.1 |
| Ubuntu:20.04:LTS | linux-oracle-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-raspi | 0 | 5.4.0-1007.7 |
| Ubuntu:20.04:LTS | linux-raspi2 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-riscv | 0 | No fix |
| Ubuntu:20.04:LTS | linux-riscv-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-riscv-5.15 | 0 | 5.15.0-1015.17~20.04.1 |
| Ubuntu:20.04:LTS | linux-riscv-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-xilinx-zynqmp | 0 | 5.4.0-1020.24 |
| Ubuntu:22.04:LTS | linux | 0 | 5.13.0-19.19 |
| Ubuntu:22.04:LTS | linux-allwinner-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-aws | 0 | 5.13.0-1005.6 |
| Ubuntu:22.04:LTS | linux-aws-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-aws-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-aws-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-aws-6.8 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-aws-6.8 | 0 | 6.8.0-1027.29~22.04.1 |
| Ubuntu:22.04:LTS | linux-azure | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-6.8 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-6.8 | 0 | 6.8.0-1027.32~22.04.1 |
| Ubuntu:22.04:LTS | linux-azure-fde | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-fde-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-fde-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-gcp | 0 | 5.13.0-1005.6 |
| Ubuntu:22.04:LTS | linux-gcp-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-gcp-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-gcp-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-gcp-6.8 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-gcp-6.8 | 0 | 6.8.0-1028.30~22.04.1 |
| Ubuntu:22.04:LTS | linux-gke | 0 | 5.15.0-1002.2 |
| Ubuntu:22.04:LTS | linux-gkeop | 0 | 5.15.0-1001.2 |
| Ubuntu:22.04:LTS | linux-hwe-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-hwe-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-hwe-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-hwe-6.8 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-hwe-6.8 | 0 | 6.8.0-58.60~22.04.1 |
| Ubuntu:22.04:LTS | linux-ibm | 0 | 5.15.0-1002.2 |
| Ubuntu:22.04:LTS | linux-ibm-6.8 | 0 | 6.8.0-1024.24~22.04.1 |
| Ubuntu:22.04:LTS | linux-intel-iot-realtime | 0 | No fix |
| Ubuntu:22.04:LTS | linux-intel-iot-realtime | 0 | 5.15.0-1021.26 |
| Ubuntu:22.04:LTS | linux-intel-iotg | 0 | 5.15.0-1004.6 |
| Ubuntu:22.04:LTS | linux-kvm | 0 | 5.13.0-1004.4 |
| Ubuntu:22.04:LTS | linux-lowlatency | 0 | 5.15.0-22.22 |
| Ubuntu:22.04:LTS | linux-lowlatency-hwe-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-lowlatency-hwe-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-lowlatency-hwe-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-lowlatency-hwe-6.8 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-lowlatency-hwe-6.8 | 0 | 6.8.0-58.60.1~22.04.1 |
| Ubuntu:22.04:LTS | linux-nvidia | 0 | 5.15.0-1005.5 |
| Ubuntu:22.04:LTS | linux-nvidia-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-nvidia-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-nvidia-6.8 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-nvidia-6.8 | 0 | 6.8.0-1026.29~22.04.1 |
| Ubuntu:22.04:LTS | linux-oem-5.17 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oem-6.0 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oem-6.1 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oem-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oracle | 0 | 5.13.0-1008.10 |
| Ubuntu:22.04:LTS | linux-oracle-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oracle-6.8 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oracle-6.8 | 0 | 6.8.0-1024.25~22.04.1 |
| Ubuntu:22.04:LTS | linux-raspi | 0 | 5.13.0-1008.9 |
| Ubuntu:22.04:LTS | linux-realtime | 0 | No fix |
| Ubuntu:22.04:LTS | linux-riscv | 0 | No fix |
| Ubuntu:22.04:LTS | linux-riscv-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-riscv-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-riscv-6.8 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-riscv-6.8 | 0 | 6.8.0-58.60.1~22.04.1 |
| Ubuntu:22.04:LTS | linux-starfive-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-starfive-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-starfive-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-xilinx-zynqmp | 0 | 5.15.0-1022.26 |
| Ubuntu:22.04:LTS:for:NVIDIA:BlueField | linux-bluefield | 0 | 5.15.0-1011.13 |
| Ubuntu:24.04:LTS | linux | 0 | No fix |
| Ubuntu:24.04:LTS | linux | 0 | 6.8.0-58.60 |
| Ubuntu:24.04:LTS | linux-aws | 0 | No fix |
| Ubuntu:24.04:LTS | linux-aws | 0 | 6.8.0-1027.29 |
| Ubuntu:24.04:LTS | linux-azure | 0 | No fix |
| Ubuntu:24.04:LTS | linux-azure | 0 | 6.8.0-1027.32 |
| Ubuntu:24.04:LTS | linux-azure-6.11 | 0 | 6.11.0-1012.12~24.04.1 |
| Ubuntu:24.04:LTS | linux-azure-fde | 0 | No fix |
| Ubuntu:24.04:LTS | linux-azure-nvidia | 0 | 6.8.0-1014.15 |
| Ubuntu:24.04:LTS | linux-gcp | 0 | No fix |
| Ubuntu:24.04:LTS | linux-gcp | 0 | 6.8.0-1028.30 |
| Ubuntu:24.04:LTS | linux-gcp-6.11 | 0 | 6.11.0-1011.11~24.04.1 |
| Ubuntu:24.04:LTS | linux-gke | 0 | No fix |
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