cve/2025/CVE-2025-37797.md

### [CVE-2025-37797](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-37797)
![](https://img.shields.io/static/v1?label=Product&message=Linux&color=blue)
![](https://img.shields.io/static/v1?label=Version&message=&color=brightgreen)
![](https://img.shields.io/static/v1?label=Version&message=21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14%20&color=brightgreen)
![](https://img.shields.io/static/v1?label=Version&message=4.14%20&color=brightgreen)
![](https://img.shields.io/static/v1?label=Vulnerability&message=n%2Fa&color=blue)

### Description

In the Linux kernel, the following vulnerability has been resolved:net_sched: hfsc: Fix a UAF vulnerability in class handlingThis patch fixes a Use-After-Free vulnerability in the HFSC qdisc classhandling. The issue occurs due to a time-of-check/time-of-use conditionin hfsc_change_class() when working with certain child qdiscs like netemor 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 queue3. The code continues assuming the queue is still non-empty, adding   the class to vttree4. This breaks HFSC scheduler assumptions that only non-empty classes   are in vttree5. Later, when the class is destroyed, this can lead to a Use-After-FreeThe fix adds a second queue length check after qdisc_peek_len() to verifythe queue wasn't emptied.

### POC

#### Reference
No PoCs from references.

#### Github
- https://github.com/w4zu/Debian_security