CVE-2026-53156 Overview
CVE-2026-53156 is a use-after-free vulnerability in the Linux kernel's nvmem (non-volatile memory) core subsystem. The flaw exists in error paths where the code calls __nvmem_device_put() — which can free the underlying memory and associated resources — and then continues to dereference the nvmem structure. Continued access to the freed object can corrupt kernel memory or destabilize the system. Upstream maintainers resolved the issue by reordering error paths so the reference to the nvmem device is released as the final step before returning the error code. The fix landed in stable trees via multiple backport commits.
Critical Impact
Use-after-free conditions in the kernel nvmem core can lead to kernel memory corruption, denial of service, or potential privilege escalation when the freed allocation is reused.
Affected Products
- Linux kernel nvmem core subsystem (multiple stable branches receiving backports)
- Distributions shipping affected kernel versions prior to the fix
- Embedded and IoT systems relying on nvmem providers and consumers
Discovery Timeline
- 2026-06-25 - CVE-2026-53156 published to NVD
- 2026-06-25 - Last updated in NVD database
Technical Details for CVE-2026-53156
Vulnerability Analysis
The Linux kernel nvmem core provides a uniform interface for non-volatile memory devices such as EEPROMs, eFuses, and OTP regions. The subsystem uses reference counting through helpers like __nvmem_device_put() to manage the lifecycle of struct nvmem_device instances. When the last reference is released, the underlying memory and associated resources can be freed.
The vulnerability stems from improper ordering of cleanup operations along error paths. The affected code calls __nvmem_device_put() before completing all uses of the nvmem structure. After the put operation, the structure may already be freed, but the function continues to access fields on the dangling pointer. This produces a classic use-after-free condition.
The upstream resolution moves every __nvmem_device_put() invocation to the last step prior to returning the error code. This ensures the structure remains valid throughout error handling.
Root Cause
The root cause is incorrect reference release ordering in error handling branches of the nvmem core. Releasing the device reference before completing dependent reads on the same structure violates object lifetime expectations. The defect is a memory safety bug in kernel C code where pointer ownership is not respected on failure paths.
Attack Vector
Exploitation requires an attacker capable of triggering the affected error paths in the nvmem core. The exact preconditions depend on the calling consumer driver and the failure scenario reached during nvmem device lookup or registration. The vulnerability is local in nature and depends on the kernel configuration, exposed nvmem consumers, and whether the freed allocation can be reclaimed by an attacker-controlled object. No public exploit is reported and the CVE carries an EPSS score of 0.168%.
The vulnerability mechanism is described in the upstream commits referenced by the Linux Kernel Commit 40e2a459c0dd, Linux Kernel Commit 5b6b6fc49189, Linux Kernel Commit cb85ef5a227b, and Linux Kernel Commit e0d38bf47a72.
Detection Methods for CVE-2026-53156
Indicators of Compromise
- Unexpected kernel oops or panic messages referencing nvmem_device functions or freed slab caches.
- KASAN (Kernel Address Sanitizer) reports flagging use-after-free reads within the nvmem core on debug kernels.
- Sporadic system instability following operations that exercise nvmem consumer or provider registration failures.
Detection Strategies
- Inventory running kernels against the stable trees that received the four backport commits and flag hosts on pre-fix versions.
- Enable KASAN and slab debugging in test environments to surface latent use-after-free reads on the nvmem path.
- Review dmesg and journald for crash signatures involving nvmem_* symbols and correlate with recent driver loads or hotplug events.
Monitoring Recommendations
- Collect and centralize kernel crash dumps and kdump artifacts for offline analysis of nvmem-related panics.
- Track package and kernel update status across the fleet to confirm patched versions are deployed.
- Alert on repeated nvmem driver probe failures, which can indicate the conditions that trigger the vulnerable error paths.
How to Mitigate CVE-2026-53156
Immediate Actions Required
- Apply the stable kernel update that includes the four upstream commits resolving the nvmem core use-after-free.
- Prioritize embedded, IoT, and edge devices that rely heavily on nvmem providers for fuses, MAC addresses, and calibration data.
- Restrict local access on systems that cannot be patched immediately, since exploitation requires local triggering of the error path.
Patch Information
The fix is available upstream and has been backported to stable trees. Reference the patch series at Linux Kernel Commit 40e2a459c0dd, Linux Kernel Commit 5b6b6fc49189, Linux Kernel Commit cb85ef5a227b, and Linux Kernel Commit e0d38bf47a72. Rebuild and redeploy custom kernels with the corresponding patch applied. Confirm distribution vendors have shipped updated kernel packages before closing remediation tickets.
Workarounds
- No vendor-supplied workaround is documented. Apply the upstream patch as the primary remediation.
- Where patching is delayed, reduce exposure by limiting untrusted local users and constraining driver loading via module signing and modules_disabled.
- For non-essential systems, disable or unload consumer drivers that exercise the affected nvmem lookup error paths when feasible.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
