REDHAT-BUG-2506217: Medium severity Mozilla Thunderbird vulnerability

Published Jul 22, 2026
·
Updated

The code to parse MIME headers for display when forwarding a message (if the setting to view all headers was enabled) had an off-by-one error, allowing a single byte to be read from the memory after the buffer for the headers, and potentially crashing Thunderbird. This vulnerability was fixed in Thunderbird 153 and Thunderbird 140.13.

Affected Software

1 affected component
Mozilla Thunderbird

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 153
  2. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 140.13

Event History

Jul 22, 2026
Data Sourced
via Red Hat·08:01 PM
DescriptionSeverityAffected Software
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Frequently Asked Questions

1

What is the severity of REDHAT-BUG-2506217?

The severity of REDHAT-BUG-2506217 is medium, rated at 4.

2

How do I fix REDHAT-BUG-2506217?

To fix REDHAT-BUG-2506217, update to the latest version of Mozilla Thunderbird as provided by your software vendor.

3

What causes the vulnerability in REDHAT-BUG-2506217?

The vulnerability in REDHAT-BUG-2506217 is caused by an off-by-one error in the code that parses MIME headers.

4

What is the impact of REDHAT-BUG-2506217?

The impact of REDHAT-BUG-2506217 can lead to a potential crash of Mozilla Thunderbird when viewing all headers.

5

Is there a workaround for REDHAT-BUG-2506217?

A workaround for REDHAT-BUG-2506217 is to disable the setting to view all headers in Mozilla Thunderbird until the fix is applied.

Contact

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