CVE-2026-84124
Use-after-free in the DOM: Core & HTML component
MEDIUM
5.4
CVSS Score
Published: September 1, 2026 at 12:18 PM UTC
Updated: September 2, 2026 at 03:12 PM UTC
2 products affected across 1 vendorFirefoxThunderbird
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Severity
MEDIUM5.4
Exploit prediction
EPSS 0.2%
SSVC
No known exploit
Description
Use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 155, Firefox ESR 140.15, and Firefox ESR 153.2.
Affected
Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.
v < 140.15.0141.0.0 ≤ v < 153.2.0154.0.0 ≤ v < 155.0.0
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 155.0.0, so it looks safe — our inference, not a vendor statement
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 yetNo remediation guidance has been written for this CVE yet. What the record does show:
Patch and advisory references
References (7)
SSVC — Action Prioritization
SSVCNo known exploitNot automatablePartial impact
SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.
CVSS
5.4MEDIUMCISA-ADP
- Attack Vector
- NETWORK
- Complexity
- LOW
- Privileges
- NONE
- User Interaction
- REQUIRED
- Scope
- UNCHANGED
- Confidentiality
- LOW
- Integrity
- LOW
- Availability
- NONE
Vector?
Quick Info
StatusANALYZED
CWE
CWE-416
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