What’s Vulnerable › Vulnerabilities

CVE-2024-40909: bpf: Fix a potential use-after-free in bpf_link_free()

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2024-07-12 · updated 2026-10-30
• Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix a potential use-after-free in bpf_link_free() After commit 1a80dbcb2dba, bpf_link can be freed by link->ops->dealloc_deferred, but the code still tests and uses link->ops->dealloc afterward, which leads to a use-after-free as reported by syzbot. Actually, one of them should be sufficient, so just call one of them instead of both. Also add a WARN_ON() in case of any problematic implementation.

Affected products

• Linux kernel: from 6.6.26 before 6.6.35; from 6.9 before 6.9.6; 6.10-rc1, 6.10-rc2 — fixed in 6.6.35, 6.9.6
• Linux: from 6.6.26 before 6.6.35; from 6.8.5 before 6.9 — fixed in 6.6.35, 6.9

How to fix

Upgrade to a fixed version: Linux kernel 6.6.35, 6.9.6; Linux 6.6.35, 6.9. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/2884dc7d08d98a89d8d65121524bb7533183a63a
• https://git.kernel.org/stable/c/91cff53136daeff50816b0baeafd38a6976f6209
• https://git.kernel.org/stable/c/e8ccda39b395169622855607085cdeef4d376e0f
• https://git.kernel.org/stable/c/fa97b8fed9896f1e89cb657513e483a152d4c382
• https://git.kernel.org/stable/c/2884dc7d08d98a89d8d65121524bb7533183a63a
• https://git.kernel.org/stable/c/91cff53136daeff50816b0baeafd38a6976f6209
• https://git.kernel.org/stable/c/fa97b8fed9896f1e89cb657513e483a152d4c382

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