CVE-2026-52930 Overview
CVE-2026-52930 is a race condition in the Linux kernel's System V shared memory subsystem (ipc/shm). The flaw resides in shm_destroy_orphaned(), which walks the shm IDR while holding only shm_ids(ns).rwsem. That lock does not serialize all fields evaluated by shm_may_destroy(). Specifically, shm_nattch is updated under shm_perm.lock, and attach paths modify it without holding the rwsem. The race can cause the kernel to treat an orphaned shared memory segment as unused while a concurrent attach is in progress. The fix moves the shm_may_destroy() check under shm_perm.lock so all destroy paths observe consistent state.
Critical Impact
A concurrent attach path racing with orphan cleanup can lead to inconsistent state for shared memory segments inside the kernel's IPC subsystem.
Affected Products
- Linux kernel — ipc/shm subsystem
- Stable kernel branches referenced by the upstream fix commits
- Distributions shipping affected kernel versions until the patch is backported
Discovery Timeline
- 2026-06-24 - CVE-2026-52930 published to NVD
- 2026-06-24 - Last updated in NVD database
Technical Details for CVE-2026-52930
Vulnerability Analysis
The vulnerability is a locking and serialization defect [CWE-362] in the System V shared memory cleanup logic. shm_destroy_orphaned() iterates the shm IDR under shm_ids(ns).rwsem and evaluates each segment with shm_may_destroy(). That helper inspects fields including shm_nattch, the attach counter that tracks active mappings. Attach paths update shm_nattch while holding only shm_perm.lock, not the rwsem. As a result, the orphan walker can observe a stale or transient value of shm_nattch and conclude that a segment is unused even when an attach is in flight. The kernel may then proceed to destroy a segment that still has, or is about to have, active attachments.
Root Cause
The root cause is inconsistent lock coverage. shm_may_destroy() reads state protected by shm_perm.lock, but shm_destroy_orphaned() invoked it under the rwsem alone. The two locks do not provide mutual exclusion against each other, so destroy decisions raced with attach-side updates.
Attack Vector
The attack vector is local. A process must be able to create, attach to, and orphan System V shared memory segments to trigger the race. No remote vector exists. The published advisory does not provide CWE assignment, CVSS metrics, or exploitation analysis beyond the kernel commit message.
No verified exploit code is available. The upstream fix is described in the kernel commits referenced below, including Kernel Git Commit 030bbc8 and Kernel Git Commit 92cda25. The patch moves the shm_may_destroy() check under shm_perm.lock and unlocks the segment when it no longer qualifies for removal, matching the locking discipline of the other destroy paths.
Detection Methods for CVE-2026-52930
Indicators of Compromise
- No public indicators of compromise are associated with CVE-2026-52930 at this time.
- Unexpected kernel warnings, oopses, or use-after-free reports referencing ipc/shm.c, shm_destroy_orphaned, or shm_may_destroy warrant investigation.
Detection Strategies
- Inventory running kernel versions across the fleet and compare against the stable branches that received the referenced commits.
- Monitor dmesg and kernel crash collectors for IPC-related faults on systems with high shared memory churn.
- Review processes that frequently create, attach to, and detach System V shared memory segments, as these workloads expose the race window.
Monitoring Recommendations
- Forward kernel logs and crash dumps to a centralized logging or SIEM platform for retention and correlation.
- Alert on repeated IPC subsystem warnings from the same host or workload.
- Track package and kernel update status to confirm patched builds are deployed.
How to Mitigate CVE-2026-52930
Immediate Actions Required
- Identify Linux hosts running kernels that predate the fix commits listed in the upstream references.
- Plan and schedule kernel upgrades to a stable release that includes the ipc/shm serialization fix.
- Reboot systems after applying kernel updates so the patched kernel is loaded.
Patch Information
The fix is delivered through the upstream Linux kernel and stable branches. Relevant commits include Kernel Git Commit 030bbc8, Kernel Git Commit 1f0d01e, Kernel Git Commit 2e5c6f4, Kernel Git Commit 6560be3, Kernel Git Commit 92cda25, Kernel Git Commit b1e9aef, Kernel Git Commit b5107b4, and Kernel Git Commit db752eb. Apply the kernel update provided by your distribution that incorporates these commits.
Workarounds
- No official workaround is documented. Apply the kernel patch as the primary remediation.
- Where patching must be deferred, restrict local access to trusted users to reduce the attack surface of the local race condition.
- Limit which workloads create and orphan large numbers of System V shared memory segments on shared multi-tenant hosts.
# Verify the running kernel version and confirm patched build is loaded
uname -r
# Example: check distribution package metadata for the kernel update
# Debian/Ubuntu
apt list --installed 2>/dev/null | grep linux-image
# RHEL/CentOS/Fedora
rpm -qa | grep kernel
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
