CVE-2026-98742
Description
A flaw was found in the Linux kernel's ALSA (Advanced Linux Sound Architecture) sequencer subsystem. A local user could exploit a race condition caused by missing locking during compatibility ioctl (input/output control) operations. By sending concurrent port creation requests, an attacker can corrupt internal port tracking and trigger a use-after-free condition when resources are released. This flaw may allow a local attacker to cause a system crash, leading to a denial of service (DoS), or potentially achieve privilege escalation.
Statement
A race condition in the ALSA sequencer compat ioctl path occurs because converted port-info requests call the common handlers without holding client ioctl_mutex. Concurrent compat CREATE_PORT operations can pass the port-count check before insertion, causing the integer port index to exceed the address field range and wrap to an existing port address. Later subscriber teardown can resolve the duplicate address to the wrong port and access a freed subscriber, creating a kernel use-after-free condition. For the CVSS the PR:L is selected because a local user with access to the ALSA sequencer device can invoke the compat ioctls without full administrative privileges. AC:H is selected because reliable triggering requires concurrent requests to hit a race window and a later teardown operation to reach the stale subscriber. The issue is not network reachable. Impact is at least a local denial of service through a kernel crash and in the worst case may include confidentiality and integrity impact or local privilege escalation due to reuse of the freed kernel object.
Mitigation
Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
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 | 4.7 | N/A | N/A |
| Attack Vector | Local | N/A | N/A |
| Attack Complexity | High | N/A | N/A |
| Privileges Required | Low | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | None | N/A | N/A |
| Integrity Impact | None | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory
The use of previously freed memory may corrupt valid data, if the memory area in question has been allocated and used properly elsewhere.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If chunk consolidation occurs after the use of previously freed data, the process may crash when invalid data is used as chunk information.
Confidentiality
Technical Impact: Read Memory
Read operations on freed memory can sometimes leak sensitive information instead of causing a crash
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If malicious data is entered before chunk consolidation can take place, it may be possible to take advantage of a write-what-where primitive to execute arbitrary code. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.
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