What is the CVSS score of CVE-2026-8946?

CVE-2026-8946 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. EPSS exploitation probability: 0.0%.

Which versions of Mozilla Firefox are affected by CVE-2026-8946?

Firefox users across the organization are vulnerable to memory disclosure attacks through specially crafted media streams, potentially exposing sensitive data such as passwords or session tokens.. A patch is available.

How to fix or mitigate CVE-2026-8946?

Within 24 hours, identify all Firefox and Firefox ESR deployments (versions before 151, ESR 115.x, and 140.x branches) in your environment. Within 7 days, deploy Firefox 151 or later to all standard installations and apply the latest security updates to ESR 115 and ESR 140 branches. Within 30 days, verify patch deployment across all endpoints using software inventory or deployment management tools and establish a baseline for Firefox version compliance monitoring.

Mozilla Firefox CVE-2026-8946

EUVD-2026-30894 HIGH

Buffer Overflow (CWE-119)

2026-05-19 mozilla

GHSA-q9p7-4943-m5gr

Buffer Overflow Mozilla

7.5

CVSS 3.1 · Vendor: mozilla

Severity by source

Vendor (mozilla) PRIMARY

7.5 HIGH

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

vuln.today AI

6.5 MEDIUM

Network-delivered via crafted web media so AV:N/AC:L/PR:N, but browser exploitation needs the victim to render the page (UI:R); impact is memory disclosure only, hence C:H/I:N/A:N.

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

4.0 AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

SUSE

HIGH

qualitative

Red Hat

7.5 HIGH

qualitative

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Lifecycle Timeline

Analysis Generated

Jul 23, 2026 - 17:50 vuln.today

CVE Published

May 19, 2026 - 12:29 nvd

UNKNOWN (no severity yet)

CVE Published

May 19, 2026 - 12:29 cve.org

HIGH 7.5

DescriptionCVE.org

Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 151, Firefox ESR 115.36, and Firefox ESR 140.11.

AnalysisAI

Out-of-bounds memory access in the Firefox Web Codecs (Audio/Video) component allows a remote attacker to disclose sensitive process memory by serving a specially crafted media stream to a victim's browser. Rated CVSS 7.5 with a confidentiality-only impact (C:H/I:N/A:N), it affects Firefox before 151 and the ESR 115.x and 140.x branches; a vendor patch is available and it carries no public exploit and a negligible EPSS score (0.04%), with CISA SSVC recording no observed exploitation.

Technical ContextAI

The flaw lives in the WebCodecs implementation, the browser API that gives web pages low-level access to individual audio and video frame encoders/decoders. CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) is the root-cause class, and the description's 'incorrect boundary conditions' phrasing combined with a confidentiality-only CVSS impact points to an out-of-bounds read rather than a write-driven code-execution bug. Codec parsing in C++ media pipelines is a classic source of boundary errors because attacker-controlled length/offset fields drive buffer indexing; here a malformed stream can push a read past the intended buffer boundary. The affected component is captured by the CPE cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* (all Firefox versions prior to the fixed releases).

RemediationAI

Vendor-released patch: upgrade to Firefox 151, Firefox ESR 115.36, or Firefox ESR 140.11, whichever matches your deployed channel, per Mozilla advisories MFSA2026-46/47/48/50/51 (https://www.mozilla.org/security/advisories/mfsa2026-46/). Enterprises on the rapid-release channel should take Firefox 151; those pinned to extended support must move to the corresponding ESR fix. On Linux, apply your distribution's rebuilt package - for example SUSE-SU-2026:2039 (https://www.suse.com/support/update/SUSE-SU-2026:2039/) or the Red Hat errata RHSA-2026:21378 through RHSA-2026:22643 (https://access.redhat.com/errata/RHSA-2026:21378). No standalone workaround is published; because the bug is in the WebCodecs media path, an interim compensating control is to restrict or block untrusted web content that exercises hardware/software media decoding (for example via enterprise policy or a proxy that filters unknown media), accepting that this can break legitimate video/audio playback and streaming sites.

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Vendor StatusVendor

SUSE

Severity: High

Product	Status
SUSE Linux Enterprise Server 12 SP5-LTSS	Fixed
SUSE Linux Enterprise Server LTSS Extended Security 12 SP5	Fixed
openSUSE Tumbleweed	Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS	Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS	Affected

CVE-2026-8946 vulnerability details – vuln.today

Back

Mozilla Firefox CVE-2026-8946

Severity by source

CVSS VectorVendor: mozilla

Lifecycle Timeline

DescriptionCVE.org

AnalysisAI

Technical ContextAI

RemediationAI

More in Mozilla

Same weakness CWE-119 – Buffer Overflow

Same technique Buffer Overflow

Vendor StatusVendor

SUSE

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External POC / Exploit Code