CVE-2026-53156 Linux Kernel NVMEM Use-After-Free Vulnerability

Technical summary

The vulnerability stems from improper resource cleanup sequencing in the NVMEM core driver. Specifically, error paths invoke __nvmem_device_put(), a function that decrements the reference count and potentially deallocates the nvmem structure and associated memory. However, the code continues to reference the nvmem structure after this function returns, creating a classic use-after-free condition (CWE-416). The fix ensures that all references to the nvmem device are released only after all dependent operations complete, reordering cleanup logic to put the device reference as the final step before returning the error code.

Business impact

Systems running affected Linux kernels face potential stability and security risks. A local attacker with user-level privileges can trigger memory corruption or information leaks, compromising system integrity and confidentiality. In multi-tenant or shared computing environments, this could enable privilege escalation or lateral movement. Organizations relying on NVMEM functionality for secure boot, firmware updates, or hardware key storage face heightened risk of supply-chain integrity attacks.

Affected systems

All Linux kernel versions incorporating the vulnerable NVMEM core code are affected. This includes distributions and devices using standard Linux kernels prior to patching. Embedded systems, IoT devices, and mobile platforms (Android) that rely on the kernel NVMEM subsystem are particularly exposed. Server and desktop distributions are affected if users have local shell access; the kernel itself is the vulnerable component, not a specific application.

Exploitability

Exploitation requires local access and unprivileged user-level execution context. No network attack vector exists. An authenticated attacker must be able to trigger NVMEM error handling paths through legitimate kernel interfaces or system calls. While the barrier to exploitation is not trivial (requires kernel API knowledge and timing), the vulnerability is not theoretical—it is a memory safety bug in core kernel code that can be triggered by deliberate probing. The lack of CISA KEV status indicates it has not been observed in active in-the-wild exploitation at the time of publication.

Remediation

Apply the upstream Linux kernel patch that restructures error handling in the NVMEM core to defer __nvmem_device_put() calls until all nvmem structure references are complete. Organizations should prioritize patching across all systems running vulnerable kernel versions, with particular attention to devices where NVMEM is actively used (secure storage, boot firmware). Verify patch deployment by confirming kernel version and backport status in distribution release notes.

Patch guidance

Consult your Linux distribution's security advisories for kernel updates addressing CVE-2026-53156. Patch availability and timelines vary by vendor (Red Hat, Canonical, SUSE, Debian, etc.); check your distribution's CVE tracker or security mailing lists. Apply patches during scheduled maintenance windows, as kernel updates typically require system reboot. For embedded and mobile devices, contact the device manufacturer or OS provider for availability. Organizations using custom or in-house kernels should backport the upstream fix from the Linux kernel repository's NVMEM subsystem commit history.

Detection guidance

Monitor system logs and kernel messages (dmesg) for NVMEM-related errors, crashes, or warnings that correlate with use-after-free conditions. Observe for unexpected memory access errors, NULL pointer dereferences, or kernel panics originating from nvmem core code paths. File integrity monitoring can detect unauthorized changes to NVMEM data storage on disk. In production, compare running kernel version against your patch baseline to identify unpatched systems. Automated vulnerability scanning tools should flag kernel versions matching affected ranges once patches are released.

Why prioritize this

This vulnerability carries a CVSS 3.1 score of 7.8 (HIGH), reflecting local attack surface, high impact on confidentiality, integrity, and availability, and no authentication requirement beyond valid user shell access. While not yet observed in active exploitation, use-after-free bugs in core kernel subsystems pose meaningful risk to system stability and data security. Prioritize patching for systems where NVMEM is actively configured or where local user access is permitted; deprioritize air-gapped or single-user systems with restricted shell access.

Risk score, explained

The score of 7.8 reflects the combination of local attack vector (AV:L), low attack complexity (AC:L), low privilege requirement (PR:L), no user interaction (UI:N), and high impact across confidentiality (C:H), integrity (I:H), and availability (A:H). The use-after-free condition can corrupt arbitrary memory, leak sensitive data, or crash the system. The lack of network reachability limits the scope but does not diminish the severity for systems with local user accounts. The absence of KEV status means active exploitation has not been tracked by CISA.

Frequently asked questions