CVE-2024-42280

What it actually does

Use-after-free in hfcmulti_tx() where *sp is dereferenced after dev_kfree_skb(*sp) has freed the skb, enabling memory corruption in the Linux kernel mISDN subsystem.

Why it matters to the business

Potential kernel crashes, denial of service, or local privilege escalation on affected Linux systems with mISDN hardware; 303 downstream dependents increase exposure across embedded and telephony environments, though low EPSS indicates limited in-the-wild risk.

How an attack unfolds

An attacker with local access or control over mISDN traffic triggers the hfcmulti_tx path to free an skb via dev_kfree_skb and then dereference the now-invalid pointer, leading to memory corruption that may be leveraged for code execution or DoS.

How to fix it

Update the Linux kernel to commit 70db2c84631f50e02e6b32b543700699dd395803 or later stable releases containing the fix; for undici package consumers apply versions 5.28.4 or 6.11.1 where applicable.

How to confirm the fix worked

Verify kernel source or binary contains the patch preventing dereference after dev_kfree_skb; confirm no vulnerable hfcmulti_tx implementation remains via code review or version checks against fixed commits.

Typical attack path

1. Obtain local access or network position to influence mISDN device handling
2. Trigger transmission path that invokes hfcmulti_tx() with a sk_buff requiring kfree
3. Cause the function to dereference the pointer after free, corrupting kernel memory
4. Exploit resulting corruption for privilege escalation or crash

How to detect it

Review kernel logs for mISDN-related oops or use-after-free warnings; inspect for unexpected skb handling in hfcmulti paths; correlate with process activity involving ISDN drivers.

What your security team should do

• Prioritize kernel updates on systems exposing mISDN interfaces within 30 days given published date and ecosystem reach
• Audit for mISDN usage in telephony or embedded deployments and disable if unused
• Monitor for new EPSS increases or KEV addition