CVE-2025-21758: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: add RCU protection to mld_newpack() mld_newpack() can be called without RTNL or RCU being held. Note that we no longer can use sock_alloc_send_skb() because ipv6.igmp_sk uses GFP_KERNEL allocations which can sleep. Instead use alloc_skb() and charge the net->ipv6.igmp_sk socket under RCU protection.

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CVSS v3.1 Score

5.5

MEDIUM

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

Affected Products

Vendor	Product	Versions
linux	linux_kernel	2.6.26 — 5.15.179
linux	linux_kernel	5.16 — 6.1.129
linux	linux_kernel	6.2 — 6.6.79
linux	linux_kernel	6.7 — 6.12.16
linux	linux_kernel	6.13 — 6.13.4
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/1b91c597b0214b1b462eb627ec02658c944623f2 https://git.kernel.org/stable/c/25195f9d5ffcc8079ad743a50c0409dbdc48d98a https://git.kernel.org/stable/c/29fa42197f26a97cde29fa8c40beddf44ea5c8f3 https://git.kernel.org/stable/c/a527750d877fd334de87eef81f1cb5f0f0ca3373 https://git.kernel.org/stable/c/d60d493b0e65647e0335e6a7c4547abcea7df8e9 https://git.kernel.org/stable/c/e8af3632a7f2da83e27b083f787bced1faba00b1

Other References

https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html https://cert-portal.siemens.com/productcert/html/ssa-082556.html

Frequently Asked Questions

What is CVE-2025-21758? +

In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: add RCU protection to mld_newpack() mld_newpack() can be called without RTNL or RCU being held. Note that we no longer can use sock_alloc_send_skb() because ipv6.igmp_sk uses GFP_KERNEL allocations which can sleep. Instead use alloc_skb() and charge the net->ipv6.igmp_sk socket under RCU protection. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-21758? +

CVE-2025-21758 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-21758? +

CVE-2025-21758 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-2025-21758? +

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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