Cyber Resilience

CVE-2025-3859

Open Redirect in Mozilla Firefox Focus ≤ 138.0

Open Redirect
Published
30 April 2025
Modified
17 June 2026
Patch / advisory
View advisory
CVSS Score v3.1 6.1
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
EPSS Score 0.0020 10th percentile
Risk Priority 45 floored blend · peak EPSS

Summary

CVE-2025-3859 is a medium-severity Open Redirect (CWE-601) vulnerability in Mozilla Firefox Focus. Its CVSS base score is 6.1 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Phishing (T1566); ranked at the 10th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) and AC-4 (Information Flow Enforcement) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A01:2025 Broken Access ControlA06:2025 Insecure Design

EU & UK References

Vulnerability Data

Websites directing users to long URLs that caused eliding to occur in the location view could leverage the truncating behavior to potentially trick users into thinking they were on a different webpage. This vulnerability was fixed in Focus 138.

CWE(s)
CWE-601CWE-451

Related Threats

MITRE ATT&CK Enterprise Techniques

T1566 Phishing Initial Access
Adversaries may send phishing messages to gain access to victim systems.
attack.mitre.org →
T1566.002 Spearphishing Link Initial Access
Adversaries may send spearphishing emails with a malicious link in an attempt to gain access to victim systems.
attack.mitre.org →
T1566.003 Spearphishing via Service Initial Access
Adversaries may send spearphishing messages via third-party services in an attempt to gain access to victim systems.
attack.mitre.org →
T1598 Phishing for Information Reconnaissance
Adversaries may send phishing messages to elicit sensitive information that can be used during targeting.
attack.mitre.org →
T1598.003 Spearphishing Link Reconnaissance
Adversaries may send spearphishing messages with a malicious link to elicit sensitive information that can be used during targeting.
attack.mitre.org →
T1534 Internal Spearphishing Lateral Movement
After they already have access to accounts or systems within the environment, adversaries may use internal spearphishing to gain access to additional information or compromise other users within the same organization.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-10290Same product: Mozilla Firefox Focus
CVE-2026-2919Same product: Mozilla Firefox Focus
CVE-2025-55032Same product: Mozilla Firefox Focus
CVE-2024-26284Same product: Mozilla Firefox Focus
CVE-2024-10474Same product: Mozilla Firefox Focus
CVE-2024-5022Same product: Mozilla Firefox Focus
CVE-2024-1563Same product: Mozilla Firefox Focus
CVE-2024-8399Same product: Mozilla Firefox Focus
CVE-2024-0605Same product: Mozilla Firefox Focus
CVE-2024-0606Same product: Mozilla Firefox Focus

Affected Assets

mozilla
firefox focus
≤ 138.0

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V3.7.2

Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation good match

Input validation directly checks and rejects untrusted redirect targets before they are used in a response.

AC-4 Information Flow Enforcement partial match

Information flow enforcement can restrict redirects to only approved/trusted destinations, stopping untrusted user-supplied URLs from being followed.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly require input validation and untrusted-redirect controls that prevent CWE-601.

PR.AT-01 partial match
prevents

User awareness training helps people recognize and avoid harm from UI misrepresentation such as phishing, but does not prevent the flaw itself.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect UI misrepresentation vulnerabilities before deployment.

A.6.3 Information security awareness, education and training partial match
prevents

Security awareness training can teach users to recognize UI misrepresentation and phishing attempts.

A.8.23 Web filtering partial match
mitigates

Preventing access to attacker-controlled or malicious sites stops users from being redirected to untrusted locations via open-redirect or phishing links.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle includes UI/UX security requirements that can prevent misrepresentation of critical information.

A.8.26 Application security requirements partial match
prevents

Application security requirements can mandate proper display and validation of critical information in the UI.

A.8.28 Secure coding partial match
prevents

Secure coding practices can prevent UI flaws that obscure or spoof critical information.

References