CVE-2025-37915: linux kernel Double Free — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: net_sched: drr: 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 drr, there won't be a UAF, but the code will add the same classifier to the list twice, which will cause memory corruption. In addition to checking for qlen being zero, this patch checks whether the class was already added to the active_list (cl_is_active) before adding to the list to cover 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

7.0

HIGH

CVSS:3.1/AV:L/AC:H/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

References

Advisories & Patches

https://git.kernel.org/stable/c/26e75716b94d6ff9be5ea07d63675c4d189f30b4 https://git.kernel.org/stable/c/2968632880f1792007eedd12eeedf7f6e2b7e9f3 https://git.kernel.org/stable/c/4b07ac06b0a712923255aaf2691637693fc7100d https://git.kernel.org/stable/c/4f0ecf50cdf76da95828578a92f130b653ac2fcf https://git.kernel.org/stable/c/5da3aad1a13e7edb8ff0778a444ccf49930313e9 https://git.kernel.org/stable/c/ab2248110738d4429668140ad22f530a9ee730e1 https://git.kernel.org/stable/c/db205b92dfe0501e5b92fb7cf00971d0e44ba3eb https://git.kernel.org/stable/c/f99a3fbf023e20b626be4b0f042463d598050c9a

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-2025-37915? +

In the Linux kernel, the following vulnerability has been resolved: net_sched: drr: 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 drr, there won't be a UAF, but the code will add the same classifier to the list twice, which will cause memory corruption. In addition to checking for qlen being zero, this patch checks whether the class was already added to the active_list (cl_is_active) before adding to the list to cover 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 7.0 (HIGH).

How severe is CVE-2025-37915? +

CVE-2025-37915 has a CVSS v3.1 score of 7.0 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-37915? +

CVE-2025-37915 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-37915? +

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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