CVE-2026-43178 procfs: fix possible double mmput() in do_procmap_query()
A double free vulnerability in the Linux kernel's procfs allows local attackers to cause a denial of service via crafted buffer sizes.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43178?
CVE-2026-43178 is a high-severity memory corruption vulnerability in Linux kernel, published on 6 May 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:
procfs: fix possible double mmput() in do_procmap_query()
When user provides incorrectly sized buffer for build ID for PROCMAP_QUERY we return with -ENAMETOOLONG error. After recent changes this condition happens later, after we unlocked mmap_lock/per-VMA lock and did mmput(), so original goto out is now wrong and will double-mmput() mm_struct. Fix by jumping further to clean up only vm_file and name_buf.
Which versions are affected by CVE-2026-43178?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43178?
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-2026-43178 being exploited?
There is no known exploitation of CVE-2026-43178 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43178, DEBIAN-CVE-2026-43178, GHSA-6xqc-j72q-x4c8, UBUNTU-CVE-2026-43178.