CVE-2026-43238 net/sched: act_skbedit: fix divide-by-zero in tcf_skbedit_hash()
A divide-by-zero error in the Linux kernel's skbedit action can cause a system crash when specific queue mapping ranges are configured.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43238?
CVE-2026-43238 is a medium-severity denial of service vulnerability in Linux kernel, published on 6 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net/sched: act_skbedit: fix divide-by-zero in tcf_skbedit_hash()
Commit 38a6f0865796 ("net: sched: support hash selecting tx queue") added SKBEDIT_F_TXQ_SKBHASH support. The inclusive range size is computed as:
mapping_mod = queue_mapping_max - queue_mapping + 1;
The range size can be 65536 when the requested range covers all possible u16 queue IDs (e.g. queue_mapping=0 and queue_mapping_max=U16_MAX). That value cannot be represented in a u16 and previously wrapped to 0, so tcf_skbedit_hash() could trigger a divide-by-zero:
queue_mapping += skb_get_hash(skb) % params->mapping_mod;
Compute mapping_mod in a wider type and reject ranges larger than U16_MAX to prevent params->mapping_mod from becoming 0 and avoid the crash.
Weakness: CWE-369
Which versions are affected by CVE-2026-43238?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43238?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-43238 being exploited?
There is no known exploitation of CVE-2026-43238 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43238, DEBIAN-CVE-2026-43238, GHSA-76w3-fgp7-3hf7, ROOT-OS-UBUNTU-2404-CVE-2026-43238, UBUNTU-CVE-2026-43238.