CVE-2026-98950 flow_dissector: avoid u16 truncation of hlen in bpf_flow_dissect()
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-98950?
CVE-2026-98950 is a vulnerability in Linux, published on 23 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
flow_dissector: avoid u16 truncation of hlen in bpf_flow_dissect()
bpf_flow_dissect() sanitizes the offsets returned by the BPF program with clamp_t(u16, ..., hlen).
If hlen is bigger than 65535, the upper bound is truncated before the comparison. For instance, with hlen == 65536, both nhoff and thoff are forced to zero, even if the program returned sane values.
This is the same class of bug as the one fixed in commit 99bda1ecbd56 ("flow_dissector: avoid u16 truncation of skb->len when computing thoff"). That fix does not cover the BPF path, because __skb_flow_dissect() returns early when a BPF flow dissector handles the packet.
struct bpf_flow_keys stores nhoff and thoff as u16, so cap hlen to U16_MAX before clamping.
Found by sashiko while reviewing the commit above.
Which versions are affected by CVE-2026-98950?
How do I fix CVE-2026-98950?
Upgrade to a fixed version.
Is CVE-2026-98950 being exploited?
There is no known exploitation of CVE-2026-98950 in the wild and no public exploit code.
Sources
Also known as AZL-110756, BELL-CVE-2026-98950, DEBIAN-CVE-2026-98950, GHSA-4jwg-g8h6-9gv7, UBUNTU-CVE-2026-98950.