CVE-2026-46253
HIGHIn 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…
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
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:
- A heap buffer overflow (OOB write) in the memcpy_fromio() calls
- 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:
- Crash with a ramoops write of less-than-record-max-size bytes.
- Reboot: ramoops registers, pstore_get_records(0) reads old crash, allocates old_log with size X
- Crash handler registered, timer started (if pstore_update_ms >= 0)
- Oops happens (non-fatal, system continues)
- pstore_dump() writes oops via ramoops_pstore_write() size Y (>X)
- pstore_new_entry = 1, pstore_timer_kick() called
- System continues running (not a panic oops)
- Timer fires after pstore_update_ms milliseconds
- pstore_timefunc() → schedule_work() → pstore_dowork() → pstore_get_records(1)
- ramoops_get_next_prz() → persistent_ram_save_old()
- buffer_size() returns Y, but old_log is X bytes
- 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.
Affected Products
linux kernellinuxDetection & mitigation playbook
Vendor / applianceDetect
Inventory every linux linux kernel deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for remote code execution at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Fix
Apply the linux linux kernel security patch or hotfix for CVE-2026-46253 on the affected version, following the vendor advisory for your exact build.
Workarounds
Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.
How O3 protects you
O3 detects and blocks CVE-2026-46253 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.
Tailored to CVE-2026-46253. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-46253 being exploited in your environment?
O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2026-46253 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.