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TI-2026-00600 Aliases CVE-2026-0818GHSA-r27j-r277-j56h

CSS-based exfiltration of the content from partially encrypted emails when allowing remote content

Priority LOW 19CWE-116Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Information disclosure, Tampering
Confidentiality · integrity · availability
Low · None · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA. Impact type from CWE-200 and CWE-352.

Summary

When a user explicitly requested Thunderbird to decrypt an inline OpenPGP message that was embedded in a text section of an email that was formatted and styled with HTML and CSS, then the decrypted contents were rendered in a context in which the CSS styles from the outer messages were active. If the user had additionally allowed loading of the remote content referenced by the outer email message, and the email was crafted by the sender using a combination of CSS rules and fonts and animations, then it was possible to extract the secret contents of the email. This vulnerability was fixed in Thunderbird 147.0.1 and Thunderbird 140.7.1.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00177 7th percentileScored 2026-11-07
Fix Fixed Thunderbird (Mozilla): 140.7.1, 147.0.1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MozillaThunderbird—140.7.1, 147.0.1Patch availableCNA
  • Thunderbird VendorMozilla Affected — Fixed in 140.7.1, 147.0.1 Patch available CNA

CPE configurations NVD · 2

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*before 140.7.1VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*before 147.0.1VulnerableMozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:* Versions before 140.7.1 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:* Versions before 147.0.1 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Thunderbird (Mozilla) Fixed in 140.7.1, 147.0.1

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 5 products
  • Red Hat Enterprise Linux 10
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-0818
  2. 2026-10-03 Alias added: GHSA-r27j-r277-j56h

References

Advisory 2

Other 1

  • TI-2024-08981 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.8
  • TI-2022-09832 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.6
  • TI-2019-08769 Improper input validation in Mozilla Firefox ESR KEVCVSS 3.1CRITICAL 10.0
  • TI-2010-03577 Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before… KEVCVSS 3.1CRITICAL 9.8
  • TI-2023-04799 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
  • TI-2023-04477 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
See all 2067 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences