CVE-2026-46253 pstore/ram: fix buffer overflow in persistent_ram_save_old()
A heap buffer overflow in the Linux kernel pstore/ram module allows attackers to potentially execute code or cause a denial of service under specific crash and reboot conditions.
- 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-2026-46253?
CVE-2026-46253 is a high-severity memory corruption vulnerability in Linux kernel, published on 3 Jun 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:
pstore/ram: fix buffer overflow in persistent_ram_save_old()
persistent_ram_save_old() can be called multiple times for the same persistent_ram_zone (e.g., via ramoops_pstore_read -> ramoops_get_next_prz for PSTORE_TYPE_DMESG records).
Currently, the function only allocates prz->old_log when it is NULL, but it unconditionally updates prz->old_log_size to the current buffer size and then performs memcpy_fromio() using this new size. If the buffer size has grown since the first allocation (which can happen across different kernel boot cycles), this leads to:
1. A heap buffer overflow (OOB write) in the memcpy_fromio() calls 2. A subsequent OOB read when ramoops_pstore_read() accesses the buffer using the incorrect (larger) old_log_size
The KASAN splat would look similar to: BUG: KASAN: slab-out-of-bounds in ramoops_pstore_read+0x... Read of size N at addr ... by task ...
The conditions are likely extremely hard to hit:
0. Crash with a ramoops write of less-than-record-max-size bytes. 1. Reboot: ramoops registers, pstore_get_records(0) reads old crash, allocates old_log with size X 2. Crash handler registered, timer started (if pstore_update_ms >= 0) 3. Oops happens (non-fatal, system continues) 4. pstore_dump() writes oops via ramoops_pstore_write() size Y (>X) 5. pstore_new_entry = 1, pstore_timer_kick() called 6. System continues running (not a panic oops) 7. Timer fires after pstore_update_ms milliseconds 8. pstore_timefunc() → schedule_work() → pstore_dowork() → pstore_get_records(1) 9. ramoops_get_next_prz() → persistent_ram_save_old() 10. buffer_size() returns Y, but old_log is X bytes 11. Y > X: memcpy_fromio() overflows heap
Requirements: - a prior crash record exists that did not fill the record size (almost impossible since the crash handler writes as much as it can possibly fit into the record, capped by max record size and the kmsg buffer almost always exceeds the max record size) - pstore_update_ms >= 0 (disabled by default) - Non-fatal oops (system survives)
Free and reallocate the buffer when the new size differs from the previously allocated size. This ensures old_log always has sufficient space for the data being copied.
Which versions are affected by CVE-2026-46253?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-46253?
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-2026-46253 being exploited?
There is no known exploitation of CVE-2026-46253 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-46253, DEBIAN-CVE-2026-46253, GHSA-rwx9-m3pj-2mv2, ROOT-OS-UBUNTU-2204-CVE-2026-46253, UBUNTU-CVE-2026-46253.