CVE-2025-37913: debian linux Double Free — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: net_sched: qfq: Fix double list add in class with netem as child qdisc As described in Gerrard's report [1], there are use cases where a netem child qdisc will make the parent qdisc's enqueue callback reentrant. In the case of qfq, there won't be a UAF, but the code will add the same classifier to the list twice, which will cause memory corruption. This patch checks whether the class was already added to the agg->active list (cl_is_active) before doing the addition to cater for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/

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CVSS v3.1 Score

7.8

HIGH

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

Weakness Type (CWE)

CWE-415 CWE-415

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.0.1 — 5.4.294
linux	linux_kernel	5.5 — 5.10.238
linux	linux_kernel	5.11 — 5.15.182
linux	linux_kernel	5.16 — 6.1.138
linux	linux_kernel	6.2 — 6.6.90
linux	linux_kernel	6.7 — 6.12.28
linux	linux_kernel	6.13 — 6.14.6
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
debian	debian_linux	All

References

Advisories & Patches

https://git.kernel.org/stable/c/005a479540478a820c52de098e5e767e63e36f0a https://git.kernel.org/stable/c/041f410aec2c1751ee22b8b73ba05d38c3a6a602 https://git.kernel.org/stable/c/0aa23e0856b7cedb3c88d8e3d281c212c7e4fbeb https://git.kernel.org/stable/c/0bf32d6fb1fcbf841bb9945570e0e2a70072c00f https://git.kernel.org/stable/c/370218e8ce711684acc4cdd3cc3c6dd7956bc165 https://git.kernel.org/stable/c/53bc0b55178bd59bdd4bcd16349505cabf54b1a2 https://git.kernel.org/stable/c/a43783119e01849fbf2fe8855634e8989b240cb4 https://git.kernel.org/stable/c/f139f37dcdf34b67f5bf92bc8e0f7f6b3ac63aa4

Other References

https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html

Frequently Asked Questions

What is CVE-2025-37913? +

In the Linux kernel, the following vulnerability has been resolved: net_sched: qfq: Fix double list add in class with netem as child qdisc As described in Gerrard's report [1], there are use cases where a netem child qdisc will make the parent qdisc's enqueue callback reentrant. In the case of qfq, there won't be a UAF, but the code will add the same classifier to the list twice, which will cause memory corruption. This patch checks whether the class was already added to the agg->active list (cl_is_active) before doing the addition to cater for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/ It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2025-37913? +

CVE-2025-37913 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-37913? +

CVE-2025-37913 affects products from debian, linux, specifically: debian_linux, linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-37913? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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