CVE-2026-93243
Received Received - Intake

Memory Exhaustion via Secretmem Unevictable Folios

Publication date: 2026-09-24

Last updated on: 2026-09-24

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: mm/secretmem: properly account locked pages secretmem accounts folios by treating memory as if it were mlock()'d and thus limited by the RLIMIT_MEMLOCK limit. However the folios are unevictable and remain so until the inode is evicted, eliminating usual mlock() semantics - mapping folios then unmapping them does not clear their unevictable state, since it depends on AS_UNEVICTABLE, not PG_mlocked. A user can therefore easily work around the RLIMIT_MEMLOCK limit - simply map then unmap and VmLck no longer counts the secretmem range. Worse, folios are not accounted in the process's RSS, meaning the OOM killer won't know to kill the process. Repeatedly mapping/unmapping (or forking) can then result in the consumption of all available system memory with unevictable folios and cause system instability. A secretmem fd can be passed between processes and over fork so a per-process limit simply does not make sense, so follow the precedent set by io_uring, perf, skbuff, iommufd and xdp by tracking the number of locked pages in user_struct->locked_vm. Since the scope tracked is actually inode lifetime, the RLIMIT_MEMLOCK applies per-user not per-process, so it doesn't make sense to bypass for users with CAP_IPC_LOCK, therefore remove this bypass. There is simply no reason to carry on marking the mapping as mlock()'d since it's misleading and the lifecycle is now correctly handled, so remove this too. Note that secretmem does not support any form of truncation (including hole punching) and the folios are unreclaimable, so the folios need only be accounted on fault and unaccounted on inode destruction. __secretmem_account_pages() is more or less a duplicate of the code that io_uring etc. use, but since this is a bug fix that needs backporting, defer any de-duplication efforts to a follow-up. test_mlock_limit() asserts mlock_future_ok() on mmap(), however this has been removed, so remove the test altogether for the fix. A new test will be sent separately for upstream.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published
2026-09-24
Last Modified
2026-09-24
Generated
2026-09-25
AI Q&A
2026-09-24
EPSS Evaluated
N/A
NVD
CVE-2026-93243
EUVD
EUVD-2026-86249

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux_kernel linux_kernel *

Helpful Resources

Exploitability

CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-UNKNOWN

Attack-Flow Graph

AI Quick Actions

Instant insights powered by AI
Executive Summary

This vulnerability in the Linux kernel involves improper accounting of locked pages in the secretmem subsystem. secretmem treats memory as if it were mlock()'d but the folios remain unevictable even after unmapping, bypassing RLIMIT_MEMLOCK limits. This allows users to consume all system memory with unevictable folios, causing instability. The fix changes how locked pages are tracked to prevent this bypass.

The issue arises because secretmem folios are not accounted in the process's RSS, so the OOM killer cannot detect or mitigate the memory consumption. Additionally, secretmem file descriptors can be shared between processes, making per-process limits ineffective.

Detection Guidance

This vulnerability is specific to the Linux kernel's secretmem implementation and does not have direct network detection methods. Monitor system memory usage and processes with high locked memory (VmLck) via commands like 'ps aux | grep -i secretmem' or 'cat /proc/meminfo'. Check for processes repeatedly mapping/unmapping memory or consuming excessive locked pages.

Impact Analysis

This vulnerability can lead to system instability or crashes by allowing a user to consume all available system memory with unevictable folios. This happens because the memory is not properly accounted for in the process's RSS, preventing the OOM killer from intervening. Repeated mapping and unmapping or forking can exacerbate the issue.

Compliance Impact

This vulnerability does not directly affect compliance with standards like GDPR or HIPAA. It primarily impacts system stability by allowing users to bypass memory limits, potentially causing denial-of-service conditions. Compliance implications would depend on how the affected system is used in a regulated environment, but the vulnerability itself is not a direct compliance violation.

Mitigation Strategies

Apply the latest Linux kernel patches addressing CVE-2026-93243. Monitor and limit user processes' locked memory usage via RLIMIT_MEMLOCK. Restrict access to secretmem functionality if not required. Review processes with high locked memory (VmLck) and terminate suspicious ones.

Chat Assistant

Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-93243. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70

EPSS Chart