What is the CVSS score of CVE-2021-33596?

CVE-2021-33596 has a CVSS 3.1 base score of 4.1 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N. EPSS exploitation probability: 0.8%.

Safe CVE-2021-33596

MEDIUM

Improper Restriction of Rendered UI Layers or Frames (CWE-1021)

2021-08-05 cve-notifications-us@f-secure.com

XSS Safe F Secure

4.1

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-1021 OWASP Top 10:2025 A06:2025 - Insecure Design ASVS 5.0 V3 - Web Frontend Security Clickjacking prevention, X-Frame-Options
Impact	CVSS score of 4.1 (MEDIUM). Attack characteristics: network attack vector, low complexity, low privileges required, user interaction required.
Exploit ScenarioDerived	This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the medium-severity affected system.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).

No patch listed yet 0.8% exploitation probability (EPSS)

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AnalysisAI

Showing the legitimate URL in the address bar while loading the content from other domain. Rated medium severity (CVSS 4.1), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

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Technical ContextAI · show details

This vulnerability is classified under CWE-1021. Showing the legitimate URL in the address bar while loading the content from other domain. This makes the user believe that the content is served by a legit domain. Exploiting the vulnerability requires the user to click on a specially crafted, seemingly legitimate URL containing an embedded malicious redirect while using F-Secure Safe Browser for iOS. Affected products include: F-Secure Safe.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 4.1 MEDIUM

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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

None

Integrity

Low

Availability

None

DescriptionNVD

Showing the legitimate URL in the address bar while loading the content from other domain. This makes the user believe that the content is served by a legit domain. Exploiting the vulnerability requires the user to click on a specially crafted, seemingly legitimate URL containing an embedded malicious redirect while using F-Secure Safe Browser for iOS.

Threat Intelligence Overview

EPSS Score

0.8%

Top 48% exploitable

Data Quality

2 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity MEDIUM

CISA KEV No

Public POC No

EPSS 0.8%

Patch available No

Active threat No

Deciding rule

MEDIUM severity (CVSS 4.0-6.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +1

CVSS: +20

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Cross-Site Scripting MEDIUM

Cross-Site Scripting occurs when an application accepts untrusted data and sends it to a web browser without proper validation or encoding.

Affected Products (CPE)NVD

cpe:2.3:a:f-secure:safe:*:*:*:*:*:iphone_os:*:*

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References

Advisories & patches

ADVISORY https://www.f-secure.com/en/business/programs/vulnerability-reward-program/hall-of-fame ADVISORY https://www.f-secure.com/en/business/support-and-downloads/security-advisories ADVISORY https://www.f-secure.com/en/business/support-and-downloads/security-advisories/cve-2021-33596

Search Externally

GitHub PoC

Exploit-DB PacketStorm Snyk Rapid7 Nuclei Templates Trickest PoC

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