# CVE-2020-1897: Use after free in proxygen

> A malicious client can trigger a use-after-free in the proxygen library via specific request error handling sequences, potentially leading to code execution or crashes.

- **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:** 18 May 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-838g-g793-hh7g

## What is CVE-2020-1897?

CVE-2020-1897 is a critical use after free vulnerability in Facebook proxygen, published on 18 May 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A use-after-free is possible due to an error in lifetime management in the request adaptor when a malicious client invokes request error handling in a specific sequence. This issue affects versions of proxygen prior to v2020.05.18.00.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2020-1897?

It affects 1 product.


Products: Facebook Proxygen.

## How do I fix CVE-2020-1897?

No fix has been published for CVE-2020-1897 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-1897 being exploited?

There is no known exploitation of CVE-2020-1897 in the wild and no public exploit code.

## Other vulnerabilities in Facebook proxygen

- [CVE-2019-11940](https://insights.sbomify.com/CVE-2019-11940/): Use after free in Proxygen (critical 9.8)
- [CVE-2019-11921](https://insights.sbomify.com/CVE-2019-11921/): Memory corruption in Proxygen (critical 9.8)
- [CVE-2018-6343](https://insights.sbomify.com/CVE-2018-6343/): Proxygen fails to validate that a secondary auth manager is set before dereferencing it. (high 7.5)
- [CVE-2025-55181](https://insights.sbomify.com/CVE-2025-55181/): Denial of service in proxygen (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-1897 and fix it if it is affected.

What it is: CVE-2020-1897 is a critical use after free vulnerability in Facebook proxygen, published on 18 May 2020. 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-2020-1897 in the wild and no public exploit code.

Affected product: Facebook proxygen. 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-2020-1897/ (Markdown: https://insights.sbomify.com/CVE-2020-1897/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1897
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1897
- OSV: https://osv.dev/vulnerability/CVE-2020-1897

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-1897/
Summaries are generated and may contain mistakes; the official description above is the record.