CVE-2025-37797
net_sched: hfsc: Fix a UAF vulnerability in class handling
Description
In the Linux kernel, the following vulnerability has been resolved: net_sched: hfsc: Fix a UAF vulnerability in class handling This patch fixes a Use-After-Free vulnerability in the HFSC qdisc class handling. The issue occurs due to a time-of-check/time-of-use condition in hfsc_change_class() when working with certain child qdiscs like netem or codel. The vulnerability works as follows: 1. hfsc_change_class() checks if a class has packets (q.qlen != 0) 2. It then calls qdisc_peek_len(), which for certain qdiscs (e.g., codel, netem) might drop packets and empty the queue 3. The code continues assuming the queue is still non-empty, adding the class to vttree 4. This breaks HFSC scheduler assumptions that only non-empty classes are in vttree 5. Later, when the class is destroyed, this can lead to a Use-After-Free The fix adds a second queue length check after qdisc_peek_len() to verify the queue wasn't emptied.
INFO
Published Date :
May 2, 2025, 3:15 p.m.
Last Modified :
Nov. 6, 2025, 8:48 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update the Linux kernel to a version that includes the fix.
- Apply the provided patch to the Linux kernel source code.
- Recompile and reinstall the kernel.
- Reboot the system to load the updated kernel.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2025-37797.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-37797 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-37797
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2025-37797 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2025-37797 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Nov. 06, 2025
Action Type Old Value New Value Added CVSS V3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Added CWE CWE-416 Added CPE Configuration OR *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.13 up to (excluding) 6.14.5 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.7 up to (excluding) 6.12.26 *cpe:2.3:o:linux:linux_kernel:6.15:rc1:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:6.15:rc2:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:6.15:rc3:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.2 up to (excluding) 6.6.89 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 4.14.1 up to (excluding) 5.4.293 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.5 up to (excluding) 5.10.237 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.11 up to (excluding) 5.15.181 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.16 up to (excluding) 6.1.136 *cpe:2.3:o:linux:linux_kernel:4.14:rc2:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:4.14:rc3:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:4.14:rc4:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:4.14:rc5:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:4.14:rc6:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:4.14:rc7:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:4.14:rc8:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:4.14:-:*:*:*:*:*:* Added CPE Configuration OR *cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:* Added Reference Type kernel.org: https://git.kernel.org/stable/c/20d584a33e480ae80d105f43e0e7b56784da41b9 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/28b09a067831f7317c3841812276022d6c940677 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/39b9095dd3b55d9b2743df038c32138efa34a9de Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/3aa852e3605000d5c47035c3fc3a986d14ccfa9f Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/3df275ef0a6ae181e8428a6589ef5d5231e58b5c Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/86cd4641c713455a4f1c8e54c370c598c2b1cee0 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/bb583c88d23b72d8d16453d24856c99bd93dadf5 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/fcc8ede663569c704fb00a702973bd6c00373283 Types: Patch Added Reference Type CVE: https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html Types: Mailing List, Third Party Advisory Added Reference Type CVE: https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html Types: Mailing List, Third Party Advisory -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Nov. 03, 2025
Action Type Old Value New Value Added Reference https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html Added Reference https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html -
New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
May. 02, 2025
Action Type Old Value New Value Added Description In the Linux kernel, the following vulnerability has been resolved: net_sched: hfsc: Fix a UAF vulnerability in class handling This patch fixes a Use-After-Free vulnerability in the HFSC qdisc class handling. The issue occurs due to a time-of-check/time-of-use condition in hfsc_change_class() when working with certain child qdiscs like netem or codel. The vulnerability works as follows: 1. hfsc_change_class() checks if a class has packets (q.qlen != 0) 2. It then calls qdisc_peek_len(), which for certain qdiscs (e.g., codel, netem) might drop packets and empty the queue 3. The code continues assuming the queue is still non-empty, adding the class to vttree 4. This breaks HFSC scheduler assumptions that only non-empty classes are in vttree 5. Later, when the class is destroyed, this can lead to a Use-After-Free The fix adds a second queue length check after qdisc_peek_len() to verify the queue wasn't emptied. Added Reference https://git.kernel.org/stable/c/20d584a33e480ae80d105f43e0e7b56784da41b9 Added Reference https://git.kernel.org/stable/c/28b09a067831f7317c3841812276022d6c940677 Added Reference https://git.kernel.org/stable/c/39b9095dd3b55d9b2743df038c32138efa34a9de Added Reference https://git.kernel.org/stable/c/3aa852e3605000d5c47035c3fc3a986d14ccfa9f Added Reference https://git.kernel.org/stable/c/3df275ef0a6ae181e8428a6589ef5d5231e58b5c Added Reference https://git.kernel.org/stable/c/86cd4641c713455a4f1c8e54c370c598c2b1cee0 Added Reference https://git.kernel.org/stable/c/bb583c88d23b72d8d16453d24856c99bd93dadf5 Added Reference https://git.kernel.org/stable/c/fcc8ede663569c704fb00a702973bd6c00373283