# CVE-2025-1933: JIT corruption of WASM i32 return values on 64-bit CPUs

> A JIT compilation flaw in Firefox and Thunderbird allows memory corruption on 64-bit CPUs, potentially enabling arbitrary code execution.

- **Severity:** High 7.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 4 Mar 2025
- **Updated:** 4 Jun 2026
- **Also known as:** DEBIAN-CVE-2025-1933, GHSA-r84f-4wj3-r6vx, UBUNTU-CVE-2025-1933

## What is CVE-2025-1933?

CVE-2025-1933 is a high-severity memory corruption vulnerability in Mozilla Firefox, published on 4 Mar 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

On 64-bit CPUs, when the JIT compiles WASM i32 return values they can pick up bits from left over memory. This can potentially cause them to be treated as a different type. This vulnerability was fixed in Firefox 136, Firefox ESR 115.21, Firefox ESR 128.8, Thunderbird 136, and Thunderbird 128.8.

## Which versions are affected by CVE-2025-1933?

It affects 2 products.


Products: Mozilla Firefox, Mozilla Thunderbird.

## How do I fix CVE-2025-1933?

Upgrade to a fixed version.

## Is CVE-2025-1933 being exploited?

There is no known exploitation of CVE-2025-1933 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-2025-1933 and fix it if it is affected.

What it is: CVE-2025-1933 is a high-severity memory corruption vulnerability in Mozilla Firefox, published on 4 Mar 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2025-1933 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-2025-1933/ (Markdown: https://insights.sbomify.com/CVE-2025-1933/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-1933
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-1933
- OSV: https://osv.dev/vulnerability/CVE-2025-1933

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-1933/
Summaries are generated and may contain mistakes; the official description above is the record.