CVE-2026-98591

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix bounds check for skb-backed dynptrs

The skb_pointer_if_linear() function checks whether a

memory region of length len starting at offset off into

the skb is in the linear area, and returns a pointer to

the region if so. The check currently subtracts between

skb_headlen and offset of the check, and since skb_headlen

is unsigned the subtraction can underflow. This causes the

bounds check to spuriously pass and generate an arbitrary

pointer of the form *(skb->data + off).

The only user of this helper is currently skb-backed BPF

dynptr code. Returning the wrong pointer leads to the

dynptr erroneously being backed with invalid memory.

Ensure the subtraction cannot underflow, and fail the check if

it would. Use u64 arithmetic to also prevent overflow when

calculating (skb_headlen(skb) - off) since off is unsigned.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References