CVE-2026-23274
Description
A flaw was found in the Linux kernel's netfilter: xt_IDLETIMER module. This vulnerability occurs when revision 0 rules attempt to reuse a timer label previously created by revision 1 with alarm timer semantics. This action can lead to calling mod_timer() on an uninitialized timer list. A local attacker could potentially trigger debug object warnings and, under certain configurations, cause a kernel panic, leading to a Denial of Service (DoS).
Statement
A denial of service condition exists in xt_IDLETIMER when a revision 0 rule reuses a timer label that was originally created by revision 1 with XT_IDLETIMER_ALARM. In that mixed revision case the reused object follows ALARM semantics and the embedded timer_list field is never initialized. A subsequent revision 0 rule insertion or replacement will still call mod_timer on the uninitialized timer_list, which triggers debugobjects warnings and can escalate to a kernel panic when panic_on_warn is enabled. The issue is not network reachable and requires local control plane access to netfilter rule management. Impact is denial of service via system crash rather than information disclosure or privilege escalation.
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 | N/A | 7.8 |
| Attack Vector | Local | N/A | Local |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | High |
| Integrity Impact | None | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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)
Confidentiality
Technical Impact: Read Memory; Read Application Data
When reusing a resource such as memory or a program variable, the original contents of that resource may not be cleared before it is sent to an untrusted party.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
The uninitialized resource may contain values that cause program flow to change in ways that the programmer did not intend.
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