CVE-2023-3776: Use-after-free in Linux kernel's net/sched: cls_fw component

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-07-21 · updated 2026-06-17
Weakness: CWE-416

Description

A use-after-free vulnerability in the Linux kernel's net/sched: cls_fw component can be exploited to achieve local privilege escalation. If tcf_change_indev() fails, fw_set_parms() will immediately return an error after incrementing or decrementing the reference counter in tcf_bind_filter(). If an attacker can control the reference counter and set it to zero, they can cause the reference to be freed, leading to a use-after-free vulnerability. We recommend upgrading past commit 0323bce598eea038714f941ce2b22541c46d488f.

Affected products

Debian Linux: 10.0, 11.0, 12.0
Linux kernel: from 2.6.12 before 4.14.322; from 4.15 before 4.19.291; from 4.20 before 5.4.251; from 5.5 before 5.10.188; from 5.11 before 5.15.121; from 5.16 before 6.1.40 — fixed in 4.14.322, 4.19.291, 5.10.188, 5.15.121, 5.4.251, 6.1.40

How to fix

Upgrade to a fixed version: Linux kernel 4.14.322, 4.19.291, 5.10.188, 5.15.121. Check the vendor advisory for mitigations.

References

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