CVE-2026-99138 tcp: fix use-after-free in do_tcp_getsockopt(TCP_CC_INFO)
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99138?
CVE-2026-99138 is a vulnerability in Linux, published on 28 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
tcp: fix use-after-free in do_tcp_getsockopt(TCP_CC_INFO)
do_tcp_getsockopt() reads icsk->icsk_ca_ops and dereferences the get_info function pointer without rcu_read_lock(). With BPF struct_ops congestion control, ca_ops can point to dynamically allocated memory that is freed concurrently, resulting in a use-after-free when the kernel dereferences or calls through the stale pointer.
BUG: KASAN: slab-use-after-free in do_tcp_getsockopt+0x2037/0x23e0 Read of size 8 at addr ffff888013701258 by task exploit/149 do_tcp_getsockopt+0x2037/0x23e0 (net/ipv4/tcp.c:4564) tcp_getsockopt+0x91/0xf0 __sys_getsockopt+0xf7/0x170
Fix this by wrapping the ca_ops load and get_info call within rcu_read_lock()/rcu_read_unlock(), and using READ_ONCE() to load the icsk_ca_ops pointer.
Which versions are affected by CVE-2026-99138?
How do I fix CVE-2026-99138?
Upgrade to a fixed version.
Is CVE-2026-99138 being exploited?
There is no known exploitation of CVE-2026-99138 in the wild and no public exploit code.
Sources
Also known as AZL-111260, BELL-CVE-2026-99138, DEBIAN-CVE-2026-99138, GHSA-xjqr-qmx4-h4w3, UBUNTU-CVE-2026-99138.