# CVE-2024-7531: Race condition in Firefox

> A race condition in NSS ChaCha20 encryption on Intel Sandy Bridge processors can leak plaintext or cause connection failures in Firefox QUIC connections.

- **Severity:** Medium 6.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Aug 2024
- **Updated:** 19 Mar 2025
- **Also known as:** DEBIAN-CVE-2024-7531, ECHO-8703-6965-c373, GHSA-3jj9-9269-99m2, ROOT-OS-DEBIAN-12-CVE-2024-7531, UBUNTU-CVE-2024-7531

## What is CVE-2024-7531?

CVE-2024-7531 is a medium-severity vulnerability in Mozilla Firefox, published on 6 Aug 2024. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Calling `PK11_Encrypt()` in NSS using CKM_CHACHA20 and the same buffer for input and output can result in plaintext on an Intel Sandy Bridge processor. In Firefox this only affects the QUIC header protection feature when the connection is using the ChaCha20-Poly1305 cipher suite. The most likely outcome is connection failure, but if the connection persists despite the high packet loss it could be possible for a network observer to identify packets as coming from the same source despite a network path change. This vulnerability affects Firefox < 129, Firefox ESR < 115.14, and Firefox ESR < 128.1.

Weakness: CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition)

## Which versions are affected by CVE-2024-7531?

It affects 2 products.


Products: Mozilla Firefox, Mozilla Firefox Esr.

## How do I fix CVE-2024-7531?

Upgrade to a fixed version.

## Is CVE-2024-7531 being exploited?

There is no known exploitation of CVE-2024-7531 in the wild and no public exploit code.

## Other vulnerabilities in Mozilla Firefox

- [CVE-2019-11708](https://insights.sbomify.com/CVE-2019-11708/): Mozilla Firefox and Thunderbird Sandbox Escape (critical 10.0, exploited in the wild)
- [CVE-2010-3765](https://insights.sbomify.com/CVE-2010-3765/): Mozilla Multiple Products Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2022-26486](https://insights.sbomify.com/CVE-2022-26486/): Mozilla Firefox Use-After-Free (critical 9.6, exploited in the wild)
- [CVE-2022-26485](https://insights.sbomify.com/CVE-2022-26485/): Mozilla Firefox Use-After-Free (high 8.8, exploited in the wild)
- [CVE-2019-11707](https://insights.sbomify.com/CVE-2019-11707/): Mozilla Firefox and Thunderbird Type Confusion (high 8.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-7531 and fix it if it is affected.

What it is: CVE-2024-7531 is a medium-severity vulnerability in Mozilla Firefox, published on 6 Aug 2024. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-7531 in the wild and no public exploit code.

Affected product: Mozilla Firefox. 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-2024-7531/ (Markdown: https://insights.sbomify.com/CVE-2024-7531/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-7531
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-7531
- OSV: https://osv.dev/vulnerability/CVE-2024-7531

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-7531/
Summaries are generated and may contain mistakes; the official description above is the record.