Linux Kernel up to 6.16.8 cancel_delayed_work use after free

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
7.7$0-$5k0.00

Summaryinfo

A vulnerability, which was classified as critical, was found in Linux Kernel up to 6.16.8. This impacts the function cancel_delayed_work. Executing a manipulation can lead to use after free. This vulnerability appears as CVE-2025-39945. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 6.16.8 and classified as critical. This vulnerability affects the function cancel_delayed_work. The manipulation with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: cnic: Fix use-after-free bugs in cnic_delete_task The original code uses cancel_delayed_work() in cnic_cm_stop_bnx2x_hw(), which does not guarantee that the delayed work item 'delete_task' has fully completed if it was already running. Additionally, the delayed work item is cyclic, the flush_workqueue() in cnic_cm_stop_bnx2x_hw() only blocks and waits for work items that were already queued to the workqueue prior to its invocation. Any work items submitted after flush_workqueue() is called are not included in the set of tasks that the flush operation awaits. This means that after the cyclic work items have finished executing, a delayed work item may still exist in the workqueue. This leads to use-after-free scenarios where the cnic_dev is deallocated by cnic_free_dev(), while delete_task remains active and attempt to dereference cnic_dev in cnic_delete_task(). A typical race condition is illustrated below: CPU 0 (cleanup) | CPU 1 (delayed work callback) cnic_netdev_event() | cnic_stop_hw() | cnic_delete_task() cnic_cm_stop_bnx2x_hw() | ... cancel_delayed_work() | /* the queue_delayed_work() flush_workqueue() | executes after flush_workqueue()*/ | queue_delayed_work() cnic_free_dev(dev)//free | cnic_delete_task() //new instance | dev = cp->dev; //use Replace cancel_delayed_work() with cancel_delayed_work_sync() to ensure that the cyclic delayed work item is properly canceled and that any ongoing execution of the work item completes before the cnic_dev is deallocated. Furthermore, since cancel_delayed_work_sync() uses __flush_work(work, true) to synchronously wait for any currently executing instance of the work item to finish, the flush_workqueue() becomes redundant and should be removed. This bug was identified through static analysis. To reproduce the issue and validate the fix, I simulated the cnic PCI device in QEMU and introduced intentional delays — such as inserting calls to ssleep() within the cnic_delete_task() function — to increase the likelihood of triggering the bug.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2025-39945 since 04/16/2025. The exploitation appears to be easy. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 01/24/2026).

The vulnerability scanner Nessus provides a plugin with the ID 269455 (Linux Distros Unpatched Vulnerability : CVE-2025-39945), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.4.300, 5.10.245, 5.15.194, 6.1.154, 6.6.108, 6.12.49 or 6.16.9 eliminates this vulnerability. Applying the patch fde6e73189f40ebcf0633aed2b68e731c25f3aa3/7b6a5b0a6b392263c3767fc945b311ea04b34bbd/0405055930264ea8fd26f4131466fa7652e5e47d/e1fcd4a9c09feac0902a65615e866dbf22616125/8eeb2091e72d75df8ceaa2172638d61b4cf8929a/6e33a7eed587062ca8161ad1f4584882a860d697/0627e1481676669cae2df0d85b5ff13e7d24c390/cfa7d9b1e3a8604afc84e9e51d789c29574fb216 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (269455) and CERT Bund (WID-SEC-2025-2194). Once again VulDB remains the best source for vulnerability data.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Google Cloud Platform
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • Open Source Linux Kernel
  • RESF Rocky Linux
  • IBM QRadar SIEM

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.9
VulDB Meta Temp Score: 7.7

VulDB Base Score: 8.0
VulDB Temp Score: 7.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 7.8
NVD Vector: 🔒

CVSSv2info

AVACAuCIA
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-DayUnlockUnlockUnlockUnlock
TodayUnlockUnlockUnlockUnlock

Nessus ID: 269455
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2025-39945

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.4.300/5.10.245/5.15.194/6.1.154/6.6.108/6.12.49/6.16.9
Patch: fde6e73189f40ebcf0633aed2b68e731c25f3aa3/7b6a5b0a6b392263c3767fc945b311ea04b34bbd/0405055930264ea8fd26f4131466fa7652e5e47d/e1fcd4a9c09feac0902a65615e866dbf22616125/8eeb2091e72d75df8ceaa2172638d61b4cf8929a/6e33a7eed587062ca8161ad1f4584882a860d697/0627e1481676669cae2df0d85b5ff13e7d24c390/cfa7d9b1e3a8604afc84e9e51d789c29574fb216

Timelineinfo

04/16/2025 CVE reserved
10/04/2025 +171 days Advisory disclosed
10/04/2025 +0 days VulDB entry created
01/24/2026 +112 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-39945 (🔒)
GCVE (CVE): GCVE-0-2025-39945
GCVE (VulDB): GCVE-100-327028
CERT Bund: WID-SEC-2025-2194 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 10/04/2025 11:32
Updated: 01/24/2026 11:14
Changes: 10/04/2025 11:32 (58), 10/08/2025 18:45 (2), 11/24/2025 02:44 (7), 12/27/2025 00:10 (1), 01/24/2026 11:14 (11)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

Discussion

No comments yet. Languages: en.

Please log in to comment.

◂ PreviousOverviewNext ▸

Interested in the pricing of exploits?

See the underground prices here!