# CVE-2021-24036: Integer overflow in HHVM

> An integer overflow in the folly library allows attackers to trigger an out-of-bounds heap write, potentially leading to remote code execution.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 23 Jul 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-67g7-384p-p2gv, UBUNTU-CVE-2021-24036

## What is CVE-2021-24036?

CVE-2021-24036 is a critical vulnerability in Facebook HHVM, published on 23 Jul 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-190 (Integer Overflow or Wraparound), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2021-24036?

It affects 2 products.


Products: Facebook Folly, Facebook Hhvm.

## How do I fix CVE-2021-24036?

No fix has been published for CVE-2021-24036 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-24036 being exploited?

There is no known exploitation of CVE-2021-24036 in the wild and no public exploit code.

## Other vulnerabilities in Facebook HHVM

- [CVE-2019-11934](https://insights.sbomify.com/CVE-2019-11934/): Memory corruption in folly (critical 9.8)
- [CVE-2018-6337](https://insights.sbomify.com/CVE-2018-6337/): Weak cryptography in HHVM (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-24036 and fix it if it is affected.

What it is: CVE-2021-24036 is a critical vulnerability in Facebook HHVM, published on 23 Jul 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-24036 in the wild and no public exploit code.

Affected product: Facebook HHVM. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-24036/ (Markdown: https://insights.sbomify.com/CVE-2021-24036/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-24036
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-24036
- OSV: https://osv.dev/vulnerability/CVE-2021-24036

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-24036/
Summaries are generated and may contain mistakes; the official description above is the record.