CVE-2025-37797
Linux Kernel HFSC Qdisc Use-After-Free Vulnerability
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 :
May 2, 2025, 3:15 p.m.
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Remotely Exploitable :
No
Impact Score :
Exploitability Score :
References to Advisories, Solutions, and Tools
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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.
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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
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.