CVE-2023-4921 - Use After Free

Severity

78%

Complexity

18%

Confidentiality

98%

A use-after-free vulnerability in the Linux kernel's net/sched: sch_qfq component can be exploited to achieve local privilege escalation. When the plug qdisc is used as a class of the qfq qdisc, sending network packets triggers use-after-free in qfq_dequeue() due to the incorrect .peek handler of sch_plug and lack of error checking in agg_dequeue(). We recommend upgrading past commit 8fc134fee27f2263988ae38920bc03da416b03d8.

CVSS 3.1 Base Score 7.8. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).

Demo Examples

Use After Free

CWE-416

The following example demonstrates the weakness.


               
}
free(buf3R2);

Use After Free

CWE-416

The following code illustrates a use after free error:


               
}
free(ptr);
logError("operation aborted before commit", ptr);

When an error occurs, the pointer is immediately freed. However, this pointer is later incorrectly used in the logError function.

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