CVE-2026-98861
Description
A flaw was found in the Linux kernel's function probe (fprobe) tracing mechanism. When handlers execute during inactive Read-Copy Update (RCU, a kernel synchronization mechanism) states, unregistration routines fail to wait for active handlers to complete before freeing memory. A privileged local attacker could exploit this flaw to trigger a use-after-free condition, leading to a Denial of Service (DoS) or potentially arbitrary code execution.
Statement
A race in fprobe unregistration can cause a use after free because standard RCU grace periods do not wait for an in flight handler that runs while RCU is not watching. An fprobe object may therefore be freed after unregister_fprobe or unregister_fprobe_async while a handler executing in an idle loop or nohz_full state still references it. The demonstrated and most likely consequence is temporal memory corruption followed by a kernel crash. For the CVSS the PR:L value in the paranoid score reflects a restricted tracing or BPF capable local process that can manage multi kprobes without full system administration rights. Typical systems restrict these operations to root or processes with CAP_BPF, CAP_PERFMON, or CAP_SYS_ADMIN, so the realistic base score uses PR:H. The race requires a narrow timing condition and handler execution while RCU is not watching, so AC:H is appropriate. The issue is local and is not network reachable.
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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