CVE-2026-23270
Description
A flaw was found in the Linux kernel. A use-after-free vulnerability exists in the traffic control act_ct path when it is incorrectly configured with non-ingress egress qdiscs (queueing disciplines). This can allow a local user with specific privileges to trigger a kernel crash, leading to a denial of service. In some cases, this vulnerability may also be exploited for privilege escalation.
Statement
A use after free risk exists in the traffic control act_ct path when it is attached to non ingress egress qdiscs. In this configuration classify can return TC_ACT_CONSUMED while the skb is still held by the defragmentation engine. That can result in the skb being consumed and later accessed again by defragmentation which may lead to a kernel crash. Impact is denial of service in the common case, but keeping in mind that a kernel UAF could be exploitable for privilege escalation in some cases. The bug could happen only if some specific configuration being used (when tc/action being used and if the act_ct linked to incorrect qdisc/block), and in some cases regular user (if with some privileges) can make such configuration. The bug is not triggerable until some specific configuration being used, so considered with limited impact level.
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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7 | N/A | 7.8 |
| Attack Vector | Local | N/A | Local |
| Attack Complexity | High | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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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