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CVE-2026-0818

19
FAUCET Score

CVE-2026-0818 describes a medium-severity vulnerability in Mozilla Thunderbird versions prior to 147.0.1 and 140.7.1. This flaw allows an attacker to potentially extract secret content from an inline OpenPGP decrypted message if the user explicitly requests decryption and has remote content loading enabled. The attack leverages crafted HTML/CSS in the outer email to style the decrypted content, with a CVSS score of 4.3 (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N). There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
< 140.7.1CPE matchmatch criteria
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*
< 147.0.1CPE matchmatch criteria
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*

CVSS Data

CVSS version used by this source: 3.1

4.3MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
NONE
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.16%
Probability of exploitation in next 30 days
EPSS Percentile
5.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0016 is in the 4th percentile among its peer group of 26,234 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (1)

mozillavendor investigatingvia nvd_reference
View patch

Vendor Advisories (1)

redhatCVE-2026-0818

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

Jan 28, 2026

References

lists.debian.org / debian-lts-announce/2026/02/msg00005.html
bugzilla.mozilla.org / show_bug.cgi
Permissions Required
mozilla.org / security/advisories/mfsa2026-07
Vendor Advisory
mozilla.org / security/advisories/mfsa2026-08
Vendor Advisory