CVE-2026-23076
Description
A flaw was found in the Linux kernel's ALSA (Advanced Linux Sound Architecture) ctxfi driver. A local user with access to the sound device and ALSA control interfaces can exploit this out-of-bounds memory access vulnerability by exercising mixer controls. This issue stems from the improper re-initialization of a loop index field, which can cause the system to access memory outside of its allocated bounds. Successful exploitation can lead to a kernel crash or unstable system behavior, resulting in a Denial of Service (DoS).
Statement
An out of bounds access can occur in the ALSA ctxfi mixer code because the rsc.conj field is used as a loop index in amixer_index and sum_index. The driver did not reliably reinitialize conj when setting up amixer and sum resources. If conj retains a stale value, the index callbacks can use it to access fixed size arrays out of range, which was observed by fuzzers and reported by UBSAN as an array index out of bounds. The issue is reachable through normal mixer control handling once the ctxfi driver is loaded. A local user with access to the sound device and ALSA control interfaces can trigger the relevant paths by exercising mixer controls. For the CVSS the PR is L because access to ALSA control devices is typically mediated by local permissions and group membership. The primary impact is availability because an out of bounds access in kernel space can crash the kernel or lead to unstable behavior.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | 7.1 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | High | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Understanding the Weakness (CWE)
Integrity,Availability
Technical Impact: DoS: Crash, Exit, or Restart
Use of an index that is outside the bounds of an array will very likely result in the corruption of relevant memory and perhaps instructions, leading to a crash, if the values are outside of the valid memory area.
Integrity
Technical Impact: Modify Memory
If the memory corrupted is data, rather than instructions, the system will continue to function with improper values.
Confidentiality,Integrity
Technical Impact: Modify Memory; Read Memory
Use of an index that is outside the bounds of an array can also trigger out-of-bounds read or write operations, or operations on the wrong objects; i.e., "buffer overflows" are not always the result. This may result in the exposure or modification of sensitive data.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If the memory accessible by the attacker can be effectively controlled, it may be possible to execute arbitrary code, as with a standard buffer overflow and possibly without the use of large inputs if a precise index can be controlled.
Integrity,Availability,Confidentiality
Technical Impact: DoS: Crash, Exit, or Restart; Execute Unauthorized Code or Commands; Read Memory; Modify Memory
A single fault could allow either an overflow (CWE-788) or underflow (CWE-786) of the array index. What happens next will depend on the type of operation being performed out of bounds, but can expose sensitive information, cause a system crash, or possibly lead to arbitrary code execution.
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