CVE-2026-84641

Information disclosure due to malicious IMAP server response

HIGH

7.5

CVSS Score

Published: September 1, 2026 at 09:33 PM UTC

Updated: September 3, 2026 at 07:14 PM UTC

1 product affected across 1 vendorThunderbird

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Severity

HIGH7.5

Exploit prediction

EPSS 0.3%

SSVC

No known exploit

Description

A malicious IMAP server can trigger use-after-free and heap-memory disclosure by sending a crafted ID response. Heap contents can ultimately be persisted to prefs.js. This vulnerability was fixed in Thunderbird 155.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Thunderbird · Mozilla

95%

v < 140.15.0141.0 ≤ v < 153.2.0154.0 ≤ v < 155.0

Vendor states this is fixed in 140.15 (unaffected)

Affected range stops below 140.15.0, so it looks safe — our inference, not a vendor statement

Vendor states this is fixed in 153.2 (unaffected)

Affected range stops below 153.2.0, so it looks safe — our inference, not a vendor statement

Vendor states this is fixed in 155 (unaffected)

Affected range stops below 155.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (4)

Permissions Required

Source: cverecord

https://bugzilla.mozilla.org/show_bug.cgi?id=2057805

Vendor Advisory

Source: cverecord

https://www.mozilla.org/security/advisories/mfsa2026-86/

Vendor Advisory

Source: cverecord

https://www.mozilla.org/security/advisories/mfsa2026-87/

Vendor Advisory

Source: cverecord

https://www.mozilla.org/security/advisories/mfsa2026-88/

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHCISA-ADP

Attack Vector: NETWORK
Complexity: LOW
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: HIGH
Integrity: NONE
Availability: NONE

Vector?

Quick Info

StatusANALYZED

CWE

CWE-416

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