CVE-2026-57963Network attack vector

Chat UI spoofing via HTML message injection

Published Jul 1, 2026 · Updated Jul 1, 2026

Cross-site scripting in Mozilla Thunderbird before 152.0.1 and ESR before 140.12.1 allows remote attackers to manipulate the chat UI. Mozilla has not disclosed the vulnerable code locus or the sanitization failure that permits HTML chat messages to inject styled content, links, and CSS. Remote attackers must be able to send HTML messages through a Matrix or XMPP chat; injected content can impersonate interface elements and present phishing links.

CVSS severity6.5
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Mozilla Thunderbird before 152.0.1 and ESR before 140.12.1 allows remote attackers to manipulate the chat UI. Mozilla has not disclosed the vulnerable code locus or the sanitization failure that permits HTML chat messages to inject styled content, links, and CSS. Remote attackers must be able to send HTML messages through a Matrix or XMPP chat; injected content can impersonate interface elements and present phishing links.

The record

CVE
CVE-2026-57963
Published
Jul 1, 2026
Updated
Jul 1, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1566.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1566.002Spearphishing Link

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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