CVE-2023-42752

What it actually does

Integer overflow in the Linux kernel causes skb_shared_info allocation to occur in userspace instead of kernel memory, exposing function pointers for attacker control on systems lacking SMAP.

Why it matters to the business

Local attackers can trigger kernel crashes leading to denial of service or attempt privilege escalation on unpatched Debian and Ubuntu systems, potentially disrupting services and requiring emergency patching across fleets.

How an attack unfolds

An attacker with local access crafts input that triggers the integer overflow during skb_shared_info handling, mapping the structure into userspace and overwriting function pointers to redirect kernel execution on systems without SMAP.

How to fix it

Upgrade Linux kernel packages to fixed versions: Debian 11/12/13 to 5.10.38-1 or later; Ubuntu 20.04 LTS to 5.4.0-77.86 or later. Reboot after installation and verify running kernel version.

How to confirm the fix worked

Confirm the installed kernel version matches or exceeds the fixed releases listed for each distribution, then test that the overflow condition no longer maps skb_shared_info into userspace.

Typical attack path

1. Obtain local user access on an affected Linux system
2. Trigger the integer overflow condition via crafted network or socket operations
3. Map skb_shared_info into userspace memory
4. Overwrite function pointers to achieve code execution or denial of service

How to detect it

Review kernel logs and audit records for unusual skb or socket allocation failures around the time of suspected activity; correlate with local user sessions attempting network or packet operations.

What your security team should do

• Prioritize patching all affected Debian and Ubuntu systems within standard change windows given the local attack vector
• Disable or restrict local user accounts where possible until patches are applied
• Monitor EPSS trend and reassess if new exploit code appears
• Apply kernel updates via distribution package managers and schedule reboots