CVE-2026-6776

Unspecified impact via WebRTC boundary error

Published Apr 21, 2026 · Updated Apr 21, 2026

Incorrect boundary conditions in Mozilla Firefox and Thunderbird before 150 allow attackers to cause unspecified impact through WebRTC. The flaw is also present in Firefox ESR and Thunderbird ESR before 140.10, but Mozilla has not disclosed the affected WebRTC networking locus or the boundary operation performed incorrectly. CISA assesses local access, no privileges, and user interaction, but conflicting downstream vectors prevent a narrower consequence statement.

CVSS severity7.8
High
EPSS probability0.11%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect boundary conditions in Mozilla Firefox and Thunderbird before 150 allow attackers to cause unspecified impact through WebRTC. The flaw is also present in Firefox ESR and Thunderbird ESR before 140.10, but Mozilla has not disclosed the affected WebRTC networking locus or the boundary operation performed incorrectly. CISA assesses local access, no privileges, and user interaction, but conflicting downstream vectors prevent a narrower consequence statement.

The record

CVE
CVE-2026-6776
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-119
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 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 vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8CISA-ADPCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer

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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