CVE-2026-23359: bpf: Fix stack-out-of-bounds write in devmap

Vulnerability summary

CVE-2026-23359 is a high (CVSS 7.8) Out-of-bounds Write vulnerability in linux. EPSS estimates a 0.14% chance of exploitation in the next 30 days, higher than 3.4% of scored vulnerabilities.

Timeline

1. 25-03-2026
   PublishedVulnerability first disclosed.
2. 15-10-2026
   Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix stack-out-of-bounds write in devmap get_upper_ifindexes() iterates over all upper devices and writes their indices into an array without checking bounds. Also the callers assume that the max number of upper devices is MAX_NEST_DEV and allocate excluded_devices[1+MAX_NEST_DEV] on the stack, but that assumption is not correct and the number of upper devices could be larger than MAX_NEST_DEV (e.g., many macvlans), causing a stack-out-of-bounds write. Add a max parameter to get_upper_ifindexes() to avoid the issue. When there are too many upper devices, return -EOVERFLOW and abort the redirect. To reproduce, create more than MAX_NEST_DEV(8) macvlans on a device with an XDP program attached using BPF_F_BROADCAST | BPF_F_EXCLUDE_INGRESS. Then send a packet to the device to trigger the XDP redirect path.

• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.