CVE-2025-21759 ipv6: mcast: extend RCU protection in igmp6_send()
A use-after-free vulnerability in the Linux kernel IPv6 multicast code allows attackers to potentially execute code or escalate privileges.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-21759?
CVE-2025-21759 is a high-severity use after free vulnerability in Linux kernel, published on 27 Feb 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ipv6: mcast: extend RCU protection in igmp6_send()
igmp6_send() can be called without RTNL or RCU being held.
Extend RCU protection so that we can safely fetch the net pointer and avoid a potential UAF.
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.
Weakness: CWE-416
Which versions are affected by CVE-2025-21759?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21759?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2025-21759 being exploited?
There is no known exploitation of CVE-2025-21759 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-58968, AZL-59064, BELL-CVE-2025-21759, DEBIAN-CVE-2025-21759, GHSA-pvj3-f5v8-hgxh, ROOT-OS-DEBIAN-11-CVE-2025-21759 and 4 more.