# CVE-2026-118175: Mozilla Thunderbird message content disclosure in reply/forward

Source: https://junglewise.ai/threats/cve-2026-118175-when-replying-to-forwarding-or-editing-a-crafted-email-message  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-27. Updated: 2026-10-27  
License: CC BY 4.0 with a link back

CVE-2026-118175 · Severity: info · Published 2026-10-27

Mozilla Thunderbird is an email client used by businesses and individuals to send and receive messages. A flaw allows attackers to craft specially designed emails that cause Thunderbird to accidentally include content from unrelated messages in reply or forwarded emails. If the user sends the compromised reply, the content of the other message is disclosed to all recipients, potentially exposing sensitive information.

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

## Quick answers

**Is CVE-2026-118175 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-118175 being exploited in the wild.

**How severe is CVE-2026-118175?** Informational severity, published 27 October 2026.

**Which products and versions are affected?** Mozilla Thunderbird before 159, before 153.6.

**Is there a fix for CVE-2026-118175?** Yes: fixed in Thunderbird 159, Thunderbird 153.6. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-118175 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-118175?** 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 159, Thunderbird 153.6

## Technical details

When a user replies to, forwards, or edits a crafted email message as a new message, Thunderbird can embed parts of a different message from the same folder into the composed message without displaying a blocked content warning. The vulnerability allows an attacker to craft a malicious email that, when replied to or forwarded by the recipient, leaks content from another message in the folder to the recipients of the reply.

## Affected products

- Mozilla Thunderbird before 159, before 153.6

## Timeline

- 2026-10-27: disclosed

## References

- [https://bugzilla.mozilla.org/show_bug.cgi?id=2081720](https://bugzilla.mozilla.org/show_bug.cgi?id=2081720)
- [https://www.mozilla.org/security/advisories/mfsa2026-121/](https://www.mozilla.org/security/advisories/mfsa2026-121/)

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