CVE-2026-43011 net/x25: Fix potential double free of skb
A double free vulnerability in the Linux kernel's X.25 network stack allows attackers to cause denial of service or potentially execute code.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43011?
CVE-2026-43011 is a critical use after free vulnerability in Linux kernel, published on 1 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net/x25: Fix potential double free of skb
When alloc_skb fails in x25_queue_rx_frame it calls kfree_skb(skb) at line 48 and returns 1 (error). This error propagates back through the call chain:
x25_queue_rx_frame returns 1 | v x25_state3_machine receives the return value 1 and takes the else branch at line 278, setting queued=0 and returning 0 | v x25_process_rx_frame returns queued=0 | v x25_backlog_rcv at line 452 sees queued=0 and calls kfree_skb(skb) again
This would free the same skb twice. Looking at x25_backlog_rcv:
net/x25/x25_in.c:x25_backlog_rcv() { ... queued = x25_process_rx_frame(sk, skb); ... if (!queued) kfree_skb(skb); }
Weakness: CWE-415
Which versions are affected by CVE-2026-43011?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43011?
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-2026-43011 being exploited?
There is no known exploitation of CVE-2026-43011 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43011, DEBIAN-CVE-2026-43011, GHSA-fprr-q2h8-xvj4, ROOT-OS-DEBIAN-11-CVE-2026-43011, ROOT-OS-UBUNTU-2204-CVE-2026-43011, ROOT-OS-UBUNTU-2404-CVE-2026-43011 and 1 more.