CVE-2021-40835

CVE-2021-40835 is a medium-severity vulnerability in F-secure Safe with a CVSS 3.x base score of 4.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Description

An URL Address bar spoofing vulnerability was discovered in Safe Browser for iOS. When user clicks on a specially crafted a malicious URL, if user does not carefully pay attention to url, user may be tricked to think content may be coming from a valid domain, while it comes from another. This is performed by using a very long username part of the url so that user cannot see the domain name. A remote attacker can leverage this to perform url address bar spoofing attack. The fix is, browser no longer shows the user name part in address bar.

Frequently asked questions

What is CVE-2021-40835?
An URL Address bar spoofing vulnerability was discovered in Safe Browser for iOS. When user clicks on a specially crafted a malicious URL, if user does not carefully pay attention to url, user may be tricked to think content may be coming from a valid domain, while it comes from another. This is performed by using a very long username part of the url so that user cannot see the domain name. A remote attacker can leverage this to perform url address bar spoofing attack. The fix is, browser no longer shows the user name part in address bar.
How severe is CVE-2021-40835?
CVE-2021-40835 has a CVSS 3.x base score of 4.6, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-40835 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-40835?
CVE-2021-40835 affects F-secure Safe. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-40835?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-40835 published?
CVE-2021-40835 was published on 2021-12-16 and last updated on 2026-06-17.

References

Affected products (1)

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