CVE-2026-89783 xfrm6: fix out-of-bounds write in xfrm6_input_addr() when secpath is full
An off-by-one error in the Linux kernel IPv6 XFRM input path allows an out-of-bounds write, potentially causing a kernel panic and denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89783?
CVE-2026-89783 is a critical memory corruption vulnerability in Linux, published on 16 Sep 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:
xfrm6: fix out-of-bounds write in xfrm6_input_addr() when secpath is full
The depth check in xfrm6_input_addr() is off by one:
if (1 + sp->len == XFRM_MAX_DEPTH) goto drop; ... sp->xvec[sp->len++] = x;
xfrm_input() can leave sp->len == XFRM_MAX_DEPTH, and the transport-mode receive path re-enters IPv6 input via xfrm_trans_reinject() with that secpath preserved. If the inner packet carries a destination-options HAO option or a type-2 routing header, xfrm6_input_addr() is called with sp->len == XFRM_MAX_DEPTH; the check (1 + 6 == 6) is false, so sp->xvec[sp->len++] writes one slot past the 6-element xvec[]. The write stays within the sec_path allocation (invisible to KASAN); UBSAN_BOUNDS flags it and panics under panic_on_warn.
Use "sp->len >= XFRM_MAX_DEPTH", matching xfrm_input(). This also restores one chain level the old check rejected at sp->len == 5.
UBSAN: array-index-out-of-bounds in net/ipv6/xfrm6_input.c:309:10 index 6 is out of range for type 'xfrm_state *[6]'
Which versions are affected by CVE-2026-89783?
How do I fix CVE-2026-89783?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-89783 being exploited?
There is no known exploitation of CVE-2026-89783 in the wild and no public exploit code.
Sources
Also known as AZL-101337, BELL-CVE-2026-89783, DEBIAN-CVE-2026-89783, GHSA-w5hj-mmmx-p42j, UBUNTU-CVE-2026-89783.