# CVE-2026-126132: Thunderbird attachment replacement disclosure via link files

Source: https://junglewise.ai/threats/cve-2026-126132-when-a-message-was-forwarded-inline-edited-as-new-or-had-an  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-10. Updated: 2026-11-10  
License: CC BY 4.0 with a link back

CVE-2026-126132 · Severity: info · Published 2026-11-10

Thunderbird, an open-source email and calendar client, failed to properly handle specially crafted attachment files (like .desktop, .url, or .lnk files) when users forwarded messages or dragged attachments into compose windows. Attackers could trick the application into replacing these attachments with local file content or data from the user's network, exposing sensitive information to message recipients or the email provider.

Technologies: [Mozilla Thunderbird](https://junglewise.ai/threats/technologies/thunderbird). Vendors: [Mozilla](https://junglewise.ai/threats/vendors/mozilla).

## Quick answers

**Is CVE-2026-126132 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-126132 being exploited in the wild.

**How severe is CVE-2026-126132?** Informational severity, published 10 November 2026.

**Which products and versions are affected?** Mozilla Thunderbird before 160.

**Is there a fix for CVE-2026-126132?** Yes: fixed in Thunderbird 160. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-126132 attacked?** It is attacked with local access.

**Am I affected by CVE-2026-126132?** Check whether you run Mozilla Thunderbird at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in Thunderbird 160

## Technical details

When a message was forwarded inline, edited as new, or had an attachment dragged into a compose window, link-type attachments (.desktop on Linux; .url or .lnk on Windows) were resolved to their target content rather than being sent as-is. Upon message save or send, the resolved content replaced the original attachment, disclosing local files or network resources. The vulnerability affects Thunderbird on Linux and Windows only; macOS and other OSes are unaffected.

## Affected products

- Mozilla Thunderbird before 160

## Timeline

- 2026-11-10: disclosed

## References

- [https://bugzilla.mozilla.org/show_bug.cgi?id=2081919](https://bugzilla.mozilla.org/show_bug.cgi?id=2081919)
- [https://www.mozilla.org/security/advisories/mfsa2026-128/](https://www.mozilla.org/security/advisories/mfsa2026-128/)

## Related threats

- [Thunderbird OAuth2 access token leak over HTTP with Exchange accounts](https://junglewise.ai/threats/cve-2026-126136-for-exchange-accounts-using-ews-or-microsoft-graph-with-oauth2)
- [Mozilla Thunderbird SMTP/POP3 response injection via STARTTLS](https://junglewise.ai/threats/cve-2026-126135-if-an-attacker-was-able-to-perform-a-man-in-the-middle-attack-on)
- [Thunderbird NTLM credential leak via feed subscription to file URL](https://junglewise.ai/threats/cve-2026-126134-thunderbird-allowed-feed-subscriptions-to-file-urls-that-point)
- [Thunderbird calendar server credentials sent to HTTP proxy](https://junglewise.ai/threats/cve-2026-126133-when-a-caldav-or-ics-calendar-was-accessed-through-an-http-proxy)
- [Thunderbird Matrix homeserver URL validation bypass](https://junglewise.ai/threats/cve-2026-118180-when-logging-in-to-a-matrix-account-thunderbird-used-the)