CVE-2025-40281 sctp: prevent possible shift-out-of-bounds in sctp_transport_update_rto
A shift-out-of-bounds error in the Linux kernel SCTP implementation allows remote attackers to cause a denial of service via crafted network packets.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-40281?
CVE-2025-40281 is a vulnerability in Linux, published on 6 Dec 2025. 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:
sctp: prevent possible shift-out-of-bounds in sctp_transport_update_rto
syzbot reported a possible shift-out-of-bounds [1]
Blamed commit added rto_alpha_max and rto_beta_max set to 1000.
It is unclear if some sctp users are setting very large rto_alpha and/or rto_beta.
In order to prevent user regression, perform the test at run time.
Also add READ_ONCE() annotations as sysctl values can change under us.
[1]
UBSAN: shift-out-of-bounds in net/sctp/transport.c:509:41 shift exponent 64 is too large for 32-bit type 'unsigned int' CPU: 0 UID: 0 PID: 16704 Comm: syz.2.2320 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:120 ubsan_epilogue lib/ubsan.c:233 [inline] __ubsan_handle_shift_out_of_bounds+0x27f/0x420 lib/ubsan.c:494 sctp_transport_update_rto.cold+0x1c/0x34b net/sctp/transport.c:509 sctp_check_transmitted+0x11c4/0x1c30 net/sctp/outqueue.c:1502 sctp_outq_sack+0x4ef/0x1b20 net/sctp/outqueue.c:1338 sctp_cmd_process_sack net/sctp/sm_sideeffect.c:840 [inline] sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1372 [inline]
Which versions are affected by CVE-2025-40281?
How do I fix CVE-2025-40281?
Apply the vendor's patch.
Is CVE-2025-40281 being exploited?
There is no known exploitation of CVE-2025-40281 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40281, DEBIAN-CVE-2025-40281, GHSA-mgqw-v2hw-3wq7, ROOT-OS-DEBIAN-12-CVE-2025-40281, ROOT-OS-DEBIAN-13-CVE-2025-40281, ROOT-OS-UBUNTU-2204-CVE-2025-40281 and 2 more.