CVE-2026-98840
Description
A flaw was found in the Linux kernel's virtual console screen driver. A race condition between virtual console write operations and console deallocation can cause the kernel to access previously freed memory, resulting in a use-after-free vulnerability. A local user could exploit this flaw to cause a Denial of Service (DoS) by crashing the system or potentially corrupt kernel memory.
Statement
A race in vcs_write can leave a stale non-NULL vc_data pointer when copy_from_user fails after the virtual console was freed during the unlocked window. The stale pointer is later passed through vcs_scr_updated to vcs_notifier, which reads vc_num from freed slab memory and produces a confirmed use-after-free read. For the CVSS the PR:L value is used because triggering requires a local user or process with access to the relevant vcs and virtual terminal interfaces, while the exact device permissions depend on the system configuration. AC:H is used because successful triggering depends on winning a race between vcs_write and virtual console deallocation. The issue is not network reachable. Impact is at least a local denial of service through a kernel warning, Oops, or crash. Limited confidentiality or integrity impact is retained only in the paranoid score because slab reuse may affect the stale read, but no controlled write or demonstrated privilege escalation primitive is present.
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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