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Linux KernelOperating system · Linux

CVE-2025-37797

HIGH · 7.8 CVSS v3.1 Published 2025-05-02
Fix available
A fix is available. Upgrade to 5.4.293 / 5.10.237 or later.
See remediation →
80/100
Remediation priority · High
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-416

Memory is used after it has been freed, so its contents — now potentially attacker-controlled — drive the program's behaviour. With careful heap grooming this becomes code execution. The fix requires disciplined ownership of memory and often a targeted rework of the object lifecycle.

General guidance for the use after free class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 4.14.1, < 5.4.293>= 5.5, < 5.10.237>= 5.11, < 5.15.181>= 5.16, < 6.1.136>= 6.2, < 6.6.89>= 6.7, < 6.12.26>= 6.13, < 6.14.5= 4.14= 6.15
Debian LinuxOperating system
Affected:= 11.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.4.293 / 5.10.237 / 5.15.181 or later
Fixed in 5.4.2935.10.2375.15.181
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux Kernel 5.4.293+, 5.10.237+, 5.15.181+, or 6.1136+ (or distribution-specific kernel package that includes the fix)

  1. 1. Identify the current running kernel version using `uname -r`
  2. 2. Check if the system is using a vulnerable kernel version based on the affected ranges: < 5.4.293, < 5.10.237, < 5.15.181, or < 6.1.136
  3. 3. For Debian 11 (bullseye), check for available kernel updates via `apt-get update && apt-get upgrade` or wait for Debian Security Advisory (DSA) for kernel packages
  4. 4. For other Linux distributions, obtain a kernel update from your vendor that includes the fix commit 20d584a33e480ae80d105f43e0e7b56784da41b9
  5. 5. Schedule a maintenance window to reboot into the updated kernel
  6. 6. After reboot, verify the new kernel version is running using `uname -r` and confirm it is >= the fixed version for your branch
Caveat Kernel upgrades may require system reboot and could introduce compatibility issues with proprietary kernel modules or specific hardware drivers; test in staging environment before production deployment

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $3,200. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-37797 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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