VulnerabilityPublished 16 Jun 2026

CVE-2026-12323: Mozilla Firefox · Clickjacking

Affects Mozilla FirefoxSource CVE Database V5

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Not known to be exploited · CVSS 5.4 Medium · patch available : update Mozilla Firefox when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

5.4Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: Low
Integrity: None
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 16 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Mozilla Firefox	Affected <152	Fixed in 152

AI-suggested

Mozilla has released an official fix for this vulnerability in Firefox version 152. Users and administrators should update affected Firefox installations to version 152 or later to remediate this issue. No additional mitigation steps are indicated or required beyond applying the official update.

Description

CVE-2026-12323 is a spoofing vulnerability in the DOM: Core & HTML component of Mozilla Firefox. This issue was addressed and fixed in Firefox version 152. The vulnerability has a medium severity with a CVSS score of 5.4. It does not have known exploits in the wild. The fix is included in the Firefox 152 release, which also addresses multiple other security vulnerabilities across various components. Users running versions prior to 152 are affected.

Impact

The vulnerability allows spoofing in the DOM Core & HTML component, which could mislead users by presenting falsified content. The impact is limited to confidentiality with no integrity or significant availability impact. There are no known exploits in the wild. The medium severity rating reflects the potential for user deception but not direct code execution or privilege escalation.

Summary

CVE-2026-12323 is a spoofing vulnerability in the DOM: Core & HTML component of Mozilla Firefox. The flaw could allow an attacker to spoof content within the browser. This vulnerability was fixed in Firefox 152. The Mozilla advisory confirms the fix and lists this issue among many other security fixes in Firefox 152 and Thunderbird 152. The CVSS 3.1 base score is 5.4, indicating a medium severity with network attack vector, low attack complexity, no privileges required, user interaction required, unchanged scope, low confidentiality impact, no integrity impact, and low availability impact.

CWE-1021Improper Restriction of Rendered UI Layers or Frames (opens in a new tab)
Base weaknessOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The web application does not restrict or incorrectly restricts frame objects or UI layers that belong to another application or domain.
Implementation
Use the "frame-ancestors" directive in the Content Security Policy, which is intended to define restrictions when it comes to allowing embedded content.
Implementation
The use of X-Frame-Options (now partially obsolete as of September 2026) allows developers of web content to restrict the usage of their application within the form of overlays, frames, or iFrames. The developer can indicate from which domains can frame the content.
Implementation
Use a "frame-breaker" script in each page that should not be framed. This is very helpful for legacy browsers that do not support the X-Frame-Options security feature previously mentioned (which is now partially obsolete).
OWASP Cheat Sheets
Content Security Policy (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V14.4.3 (opens in a new tab)
V14.4.7 (opens in a new tab)
Attack patterns
Clickjacking (opens in a new tab)
Flash File Overlay (opens in a new tab)
iFrame Overlay (opens in a new tab)
Task Impersonation (opens in a new tab)
Tapjacking (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 23 Jun 2026, 15:19 UTC

WeaknessesCWE-1021

Technical details

References

Community reviews

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