CVE-2025-37797

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Source
https://cve.org/CVERecord?id=CVE-2025-37797
Import Source
https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-37797.json
JSON Data
https://api.test.osv.dev/v1/vulns/CVE-2025-37797
Downstream
Related
Published
2025-05-02T14:16:01.905Z
Modified
2026-03-20T12:42:28.253Z
Summary
net_sched: hfsc: Fix a UAF vulnerability in class handling
Details

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 hfscchangeclass() when working with certain child qdiscs like netem or codel.

The vulnerability works as follows: 1. hfscchangeclass() checks if a class has packets (q.qlen != 0) 2. It then calls qdiscpeeklen(), 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 qdiscpeeklen() to verify the queue wasn't emptied.

Database specific 
{
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/37xxx/CVE-2025-37797.json"
}
References

Affected packages

Git / git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

Affected ranges

Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14
Fixed
28b09a067831f7317c3841812276022d6c940677
Fixed
39b9095dd3b55d9b2743df038c32138efa34a9de
Fixed
fcc8ede663569c704fb00a702973bd6c00373283
Fixed
20d584a33e480ae80d105f43e0e7b56784da41b9
Fixed
3aa852e3605000d5c47035c3fc3a986d14ccfa9f
Fixed
86cd4641c713455a4f1c8e54c370c598c2b1cee0
Fixed
bb583c88d23b72d8d16453d24856c99bd93dadf5
Fixed
3df275ef0a6ae181e8428a6589ef5d5231e58b5c

Database specific

source 
"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-37797.json"