Firefox: User Interface (UI) Misrepresentation of Critical Information
CVE-2026-109736 is a high-severity user interface (UI) misrepresentation of critical information vulnerability in Firefox from Mozilla, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. There is no confirmed exploitation so far. EPSS estimates a 0.34% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of Firefox you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on mozilla.org for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Mozilla | Firefox | Not specified in the record | Not stated |
| Mozilla | Thunderbird | Not specified in the record | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N. Scored by CISA (ADP).
Official description
Frame poisoning in the Layout component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, Thunderbird 153.5, and Firefox ESR 115.45.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: User Interface (UI) Misrepresentation of Critical Information
The user interface (UI) does not properly represent critical information to the user, allowing the information - or its source - to be obscured or spoofed. This is often a component in phishing attacks.
How developers prevent this class of flaw
- Perform data validation (e.g. syntax, length, etc.) before interpreting the data.
- Create a strategy for presenting information, and plan for how to display unusual characters.
More User Interface (UI) Misrepresentation of Critical Information vulnerabilities (CWE-451)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other references
Other vulnerabilities in Firefox
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
Recent User Interface (UI) Misrepresentation of Critical Information vulnerabilities
- 8.1 High severity
- 7.4 High severity
- 7.4 High severity
- 8.1 High severity
- 7.5 High severity
- 8.0 High severity
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