# CVE-2025-3932: Tracking Links in Attachments Bypassed Remote Content Blocking

> Attackers can bypass remote content blocking in Thunderbird by crafting emails with tracking links disguised as attachments, automatically triggering web requests.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N`)
- **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:** 14 May 2025
- **Updated:** 13 Apr 2026
- **Also known as:** DEBIAN-CVE-2025-3932, GHSA-jfxg-6gv4-f2gh, UBUNTU-CVE-2025-3932

## What is CVE-2025-3932?

CVE-2025-3932 is a medium-severity vulnerability in Mozilla Thunderbird, published on 14 May 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

It was possible to craft an email that showed a tracking link as an attachment. If the user attempted to open the attachment, Thunderbird automatically accessed the link. The configuration to block remote content did not prevent that. Thunderbird has been fixed to no longer allow access to web pages listed in the X-Mozilla-External-Attachment-URL header of an email. This vulnerability was fixed in Thunderbird 128.10.1 and Thunderbird 138.0.1.

Weakness: CWE-288 (Authentication Bypass Using an Alternate Path or Channel)

## Which versions are affected by CVE-2025-3932?

It affects 1 product.


Products: Mozilla Thunderbird.

## How do I fix CVE-2025-3932?

Upgrade to a fixed version.

## Is CVE-2025-3932 being exploited?

There is no known exploitation of CVE-2025-3932 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-2025-3932 and fix it if it is affected.

What it is: CVE-2025-3932 is a medium-severity vulnerability in Mozilla Thunderbird, published on 14 May 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-2025-3932 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-2025-3932/ (Markdown: https://insights.sbomify.com/CVE-2025-3932/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-3932
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-3932
- OSV: https://osv.dev/vulnerability/CVE-2025-3932

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-3932/
Summaries are generated and may contain mistakes; the official description above is the record.