CVE-2026-23052 ftrace: Do not over-allocate ftrace memory
A logic error in Linux kernel ftrace memory allocation causes excessive page usage and kernel warnings, potentially leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-23052?
CVE-2026-23052 is a denial of service vulnerability in Linux, published on 4 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:
ftrace: Do not over-allocate ftrace memory
The pg_remaining calculation in ftrace_process_locs() assumes that ENTRIES_PER_PAGE multiplied by 2^order equals the actual capacity of the allocated page group. However, ENTRIES_PER_PAGE is PAGE_SIZE / ENTRY_SIZE (integer division). When PAGE_SIZE is not a multiple of ENTRY_SIZE (e.g. 4096 / 24 = 170 with remainder 16), high-order allocations (like 256 pages) have significantly more capacity than 256 * 170. This leads to pg_remaining being underestimated, which in turn makes skip (derived from skipped - pg_remaining) larger than expected, causing the WARN(skip != remaining) to trigger.
Extra allocated pages for ftrace: 2 with 654 skipped WARNING: CPU: 0 PID: 0 at kernel/trace/ftrace.c:7295 ftrace_process_locs+0x5bf/0x5e0
A similar problem in ftrace_allocate_records() can result in allocating too many pages. This can trigger the second warning in ftrace_process_locs().
Extra allocated pages for ftrace WARNING: CPU: 0 PID: 0 at kernel/trace/ftrace.c:7276 ftrace_process_locs+0x548/0x580
Use the actual capacity of a page group to determine the number of pages to allocate. Have ftrace_allocate_pages() return the number of allocated pages to avoid having to calculate it. Use the actual page group capacity when validating the number of unused pages due to skipped entries. Drop the definition of ENTRIES_PER_PAGE since it is no longer used.
Which versions are affected by CVE-2026-23052?
How do I fix CVE-2026-23052?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-23052 being exploited?
There is no known exploitation of CVE-2026-23052 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-23052, DEBIAN-CVE-2026-23052, GHSA-qvpg-9fvc-x6cv, UBUNTU-CVE-2026-23052.