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CVE-2026-100821

Site isolation issue in the Panning and Zooming component

MEDIUM
4.7
CVSS Score
Published: September 29, 2026 at 12:36 PM UTC
Updated: October 13, 2026 at 05:13 PM UTC
2 products affected across 1 vendorFirefoxThunderbird

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Severity
MEDIUM4.7
Exploit prediction
EPSS 0.1%
SSVC
No known exploit

Description

Site isolation issue in the Panning and Zooming component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

Affected

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

Firefox· Mozilla
95%
v < 115.42.0116.0.0 ≤ v < 140.17.0141.0.0 ≤ v < 153.4.0154.0.0 ≤ v < 157.0.0
Vendor states this is fixed in 115.42 (unaffected)
Vendor states this is fixed in 140.17 (unaffected)
Vendor states this is fixed in 153.4 (unaffected)
Vendor states this is fixed in 157 (unaffected)
Thunderbird· Mozilla
95%
v < 140.17.0141.0 ≤ v < 153.4.0154.0 ≤ v < 157.0
Vendor states this is fixed in 140.17 (unaffected)
Vendor states this is fixed in 153.4 (unaffected)
Vendor states this is fixed in 157 (unaffected)

References (8)

Permissions Required
Source: cverecord
https://bugzilla.mozilla.org/show_bug.cgi?id=2071784
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-100/
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-97/
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-98/
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-99/
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-101/
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-102/
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-103/

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

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

CVSS

4.7MEDIUMCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-346

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