CVE-2026-23199 procfs: avoid fetching build ID while holding VMA lock
A race condition in the Linux kernel procfs subsystem can cause a deadlock, leading to a denial of service.
- 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-2026-23199?
CVE-2026-23199 is a medium-severity vulnerability in Linux kernel, published on 14 Feb 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: avoid fetching build ID while holding VMA lock
Fix PROCMAP_QUERY to fetch optional build ID only after dropping mmap_lock or per-VMA lock, whichever was used to lock VMA under question, to avoid deadlock reported by syzbot:
-> #1 (&mm->mmap_lock){++++}-{4:4}: __might_fault+0xed/0x170 _copy_to_iter+0x118/0x1720 copy_page_to_iter+0x12d/0x1e0 filemap_read+0x720/0x10a0 blkdev_read_iter+0x2b5/0x4e0 vfs_read+0x7f4/0xae0 ksys_read+0x12a/0x250 do_syscall_64+0xcb/0xf80 entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (&sb->s_type->i_mutex_key#8){++++}-{4:4}: __lock_acquire+0x1509/0x26d0 lock_acquire+0x185/0x340 down_read+0x98/0x490 blkdev_read_iter+0x2a7/0x4e0 __kernel_read+0x39a/0xa90 freader_fetch+0x1d5/0xa80 __build_id_parse.isra.0+0xea/0x6a0 do_procmap_query+0xd75/0x1050 procfs_procmap_ioctl+0x7a/0xb0 __x64_sys_ioctl+0x18e/0x210 do_syscall_64+0xcb/0xf80 entry_SYSCALL_64_after_hwframe+0x77/0x7f
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- rlock(&mm->mmap_lock); lock(&sb->s_type->i_mutex_key#8); lock(&mm->mmap_lock); rlock(&sb->s_type->i_mutex_key#8);
*** DEADLOCK ***
This seems to be exacerbated (as we haven't seen these syzbot reports before that) by the recent:
777a8560fd29 ("lib/buildid: use __kernel_read() for sleepable context")
To make this safe, we need to grab file refcount while VMA is still locked, but other than that everything is pretty straightforward. Internal build_id_parse() API assumes VMA is passed, but it only needs the underlying file reference, so just add another variant build_id_parse_file() that expects file passed directly.
[akpm@linux-foundation.org: fix up kerneldoc]
Weakness: CWE-667
Which versions are affected by CVE-2026-23199?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-23199?
Apply the vendor's patch.
Is CVE-2026-23199 being exploited?
There is no known exploitation of CVE-2026-23199 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-23199, DEBIAN-CVE-2026-23199, GHSA-hjgx-24cq-764x, ROOT-OS-DEBIAN-13-CVE-2026-23199, UBUNTU-CVE-2026-23199.