# CVE-2025-3522: Leak of hashed Window credentials via crafted attachment URL

> Attackers can leak hashed Windows credentials by crafting external attachment URLs in emails, affecting Thunderbird users.

- **Severity:** Medium 6.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L`)
- **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:** 15 Apr 2025
- **Updated:** 13 Apr 2026
- **Also known as:** DEBIAN-CVE-2025-3522, GHSA-78fw-w53r-pgwg, UBUNTU-CVE-2025-3522

## What is CVE-2025-3522?

CVE-2025-3522 is a medium-severity server-side request forgery vulnerability in Mozilla Thunderbird, published on 15 Apr 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

Thunderbird processes the X-Mozilla-External-Attachment-URL header to handle attachments which can be hosted externally. When an email is opened, Thunderbird accesses the specified URL to  determine file size, and navigates to it when the user clicks the attachment. Because the URL is not validated or sanitized, it can reference internal resources like chrome:// or SMB share file:// links, potentially leading to hashed Windows credential leakage and opening the door to more serious security issues. This vulnerability was fixed in Thunderbird 137.0.2 and Thunderbird 128.9.2.

Weakness: CWE-601 (URL Redirection to Untrusted Site)

## Which versions are affected by CVE-2025-3522?

It affects 1 product.


Products: Mozilla Thunderbird.

## How do I fix CVE-2025-3522?

Upgrade to a fixed version.

## Is CVE-2025-3522 being exploited?

There is no known exploitation of CVE-2025-3522 in the wild and no public exploit code.

## Other vulnerabilities in Mozilla Thunderbird

- [CVE-2026-92238](https://insights.sbomify.com/CVE-2026-92238/): Ambiguous parsing of mail headers (critical 9.8)
- [CVE-2026-84637](https://insights.sbomify.com/CVE-2026-84637/): Calendar invitation attachments could launch local executables (critical 9.8)
- [CVE-2021-43529](https://insights.sbomify.com/CVE-2021-43529/): Memory corruption in Thunderbird (critical 9.8)
- [CVE-2019-11703](https://insights.sbomify.com/CVE-2019-11703/): Memory corruption in Thunderbird (critical 9.8)
- [CVE-2019-11704](https://insights.sbomify.com/CVE-2019-11704/): Memory corruption in Thunderbird (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-3522 and fix it if it is affected.

What it is: CVE-2025-3522 is a medium-severity server-side request forgery vulnerability in Mozilla Thunderbird, published on 15 Apr 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-2025-3522 in the wild and no public exploit code.

Affected product: Mozilla Thunderbird. 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-2025-3522/ (Markdown: https://insights.sbomify.com/CVE-2025-3522/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-3522
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-3522
- OSV: https://osv.dev/vulnerability/CVE-2025-3522

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-3522/
Summaries are generated and may contain mistakes; the official description above is the record.