CVE-2026-46088: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-46088 Overview

CVE-2026-46088 is a Linux kernel vulnerability in the Advanced Linux Sound Architecture (ALSA) control subsystem. The flaw resides in snd_ctl_elem_init_enum_names(), which advances a pointer through the enum names buffer while decrementing buf_len. When buf_len reaches zero with items still remaining, the next iteration calls strnlen(p, 0), triggering a fortified bounds check failure under CONFIG_FORTIFY_SOURCE.

The issue was discovered through kernel fuzz testing performed via Xiaomi Smartphone. The fix adds a buf_len == 0 guard at the loop entry to prevent invoking the fortified strnlen() on an exhausted buffer.

Critical Impact
When Clang loses track of the object size for pointer p inside the loop, the fortified strnlen() triggers a BRK exception panic, leading to a kernel denial of service.

Affected Products

Linux kernel versions containing the ALSA control subsystem with snd_ctl_elem_init_enum_names()
Builds compiled with CONFIG_FORTIFY_SOURCE enabled
Kernels built using Clang where dynamic object size tracking may degrade inside the loop

Discovery Timeline

2026-05-27 - CVE-2026-46088 published to NVD
2026-05-27 - Last updated in NVD database

Technical Details for CVE-2026-46088

Vulnerability Analysis

The vulnerability resides in snd_ctl_elem_init_enum_names() within the Linux kernel ALSA control subsystem. This function iterates through a names buffer containing enumerated string entries used to describe ALSA control elements. During each iteration, it advances pointer p past the current name and decrements buf_len by the consumed length.

The defect occurs when buf_len reaches zero while items remain to be processed. The next loop iteration calls strnlen(p, 0) on the exhausted buffer. While the unfortified strnlen would return zero and fall into the existing name_len == 0 error path, kernels built with CONFIG_FORTIFY_SOURCE route the call through a fortified wrapper.

The fortified strnlen() first validates maxlen against __builtin_dynamic_object_size(). When Clang loses track of the object size of p inside the loop, the fortify check fires before the return value is ever evaluated, raising a BRK exception and panicking the kernel.

Root Cause

The root cause is missing input validation at the loop entry. The function does not check whether buf_len has been exhausted before invoking strnlen(), allowing the fortified bounds check to fire on a zero-length read against a pointer with indeterminate object size.

Attack Vector

A local actor able to supply crafted enum name data to the ALSA control interface can trigger the condition. The flaw was reproduced through kernel fuzz testing on Xiaomi Smartphone hardware, demonstrating that malformed input from userspace pathways feeding snd_ctl_elem_init_enum_names() can panic the kernel.

No verified exploitation code is available. The vulnerability manifests as a fortify-induced BRK exception when fed an enum names buffer whose declared item count exceeds the actual buffer length. Refer to the upstream kernel commits for the exact patched code path.

Detection Methods for CVE-2026-46088

Indicators of Compromise

Unexpected kernel panics referencing snd_ctl_elem_init_enum_names in the stack trace
BRK exception messages tied to fortified strnlen() in kernel logs (dmesg)
Repeated ALSA control ioctl calls from low-privilege processes preceding a kernel crash

Detection Strategies

Monitor kernel ring buffer and journalctl -k output for fortify-source panic signatures involving ALSA symbols
Inspect crash dumps and kdump artifacts for call stacks traversing snd_ctl_elem_add paths into snd_ctl_elem_init_enum_names
Correlate unprivileged process activity against /dev/snd/control* device access immediately preceding kernel faults

Monitoring Recommendations

Aggregate kernel logs centrally and alert on fortify-source BRK exceptions
Track host reboot patterns to surface clusters of ALSA-related panics across the fleet
Audit which workloads or containers hold access to /dev/snd device nodes and reduce exposure where unnecessary

How to Mitigate CVE-2026-46088

Immediate Actions Required

Apply the upstream Linux kernel patches referenced in the kernel.org commits for snd_ctl_elem_init_enum_names()
Rebuild and redeploy any custom kernels that include the ALSA control subsystem, particularly those built with Clang and CONFIG_FORTIFY_SOURCE
Restrict access to /dev/snd/control* interfaces to trusted user accounts and service principals

Patch Information

Fixes have been merged across multiple stable branches. Reference the upstream commits: 1fbe46d2b727, 654c818a69c2, 82012fd3e78a, 8ba0214c3dd3, and e0da8a8cac74. The fix introduces a buf_len == 0 guard at loop entry so the fortified strnlen() is never invoked on an exhausted buffer.

Workarounds

Where patching is not yet possible, restrict unprivileged access to ALSA control device nodes through filesystem permissions or device cgroups
Disable or unload the ALSA control interface on hosts that do not require audio functionality
In containerized environments, avoid mapping /dev/snd into untrusted workloads

bash

# Verify kernel version and confirm patched commit is present
uname -r

# Restrict access to ALSA control device nodes
chmod 0660 /dev/snd/control*
chown root:audio /dev/snd/control*

# In container runtimes, do not expose /dev/snd to untrusted workloads
# Example: ensure docker run is NOT invoked with: --device /dev/snd