CVE-2026-98856 kprobes: Skip disarmed probes when checking optkprobe overlap
A local attacker with high privileges can trigger memory corruption in the Linux kernel kprobes subsystem, potentially leading to arbitrary code execution or privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98856?
CVE-2026-98856 is a memory corruption vulnerability in Linux, published on 18 Oct 2026. 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:
kprobes: Skip disarmed probes when checking optkprobe overlap
On x86, an optkprobe at A replaces five bytes with a jump. If a disabled probe B is at A+2, get_optimized_kprobe() stops at B when arming a new probe C at A+4. It leaves A optimized:
A A+1 A+2 A+3 A+4 A's jump | e9 | d0 | d1 | d2 | d3 | after C | e9 | d0 | d1 | d2 | cc |
The INT3 for C overwrites the last byte of A's jump displacement, so execution can jump to the wrong address. B can have prepared optinsns while disarmed, but has no jump to unoptimize.
Continue past disarmed and unprepared probes to find the active optimized probe before arming a probe in its jump.
Which versions are affected by CVE-2026-98856?
How do I fix CVE-2026-98856?
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-2026-98856 being exploited?
There is no known exploitation of CVE-2026-98856 in the wild and no public exploit code.
Sources
Also known as AZL-108723, BELL-CVE-2026-98856, DEBIAN-CVE-2026-98856, GHSA-9hm5-vfv2-whh5, UBUNTU-CVE-2026-98856.