How severe is CVE-2021-3639?

CVE-2021-3639 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-3639 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3639?

CVE-2021-3639 affects Uninett Mod Auth Mellon. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3639?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-3639 published?

CVE-2021-3639 was published on 2022-08-22 and last updated on 2026-06-17.

CVE-2021-3639

CVE-2021-3639 is a medium-severity vulnerability in Uninett Mod Auth Mellon with a CVSS 3.x base score of 6.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-601.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
EPSS exploit prediction: 1% (51st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-601
Affected product: Uninett Mod Auth Mellon
Published: 2022-08-22
Last modified: 2026-06-17

Description

A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue could be used by an attacker to facilitate phishing attacks by tricking users into visiting a trusted web application URL that redirects to an external and potentially malicious server. The highest threat from this liability is to confidentiality and integrity.

Frequently asked questions

What is CVE-2021-3639?: A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue could be used by an attacker to facilitate phishing attacks by tricking users into visiting a trusted web application URL that redirects to an external and potentially malicious server. The highest threat from this liability is to confidentiality and integrity.
How severe is CVE-2021-3639?: CVE-2021-3639 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-3639 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3639?: CVE-2021-3639 affects Uninett Mod Auth Mellon. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3639?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-3639 published?: CVE-2021-3639 was published on 2022-08-22 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:uninett:mod_auth_mellon:*:*:*:*:*:*:*:*

More vulnerabilities in Uninett Mod Auth Mellon

CVE-2014-8567 — Critical (CVSS 9.4): The mod_auth_mellon module before 0.8.1 allows remote attackers to cause a denial of service (Apache HTTP server crash)…
CVE-2016-2146 — High (CVSS 7.5): The am_read_post_data function in mod_auth_mellon before 0.11.1 does not limit the amount of data read, which allows…
CVE-2016-2145 — High (CVSS 7.5): The am_read_post_data function in mod_auth_mellon before 0.11.1 does not check if the ap_get_client_block function…
CVE-2014-8566 — Medium (CVSS 6.4): The mod_auth_mellon module before 0.8.1 allows remote attackers to obtain sensitive information or cause a denial of…
CVE-2017-6807 — Medium (CVSS 6.1): mod_auth_mellon before 0.13.1 is vulnerable to a Cross-Site Session Transfer attack, where a user with access to one…

All CVEs affecting Uninett Mod Auth Mellon →

Other CWE-601 (Open Redirect) vulnerabilities

CVE-2018-3774 — Critical (CVSS 10.0): Incorrect parsing in url-parse <1.4.3 returns wrong hostname which leads to multiple vulnerabilities such as SSRF, Open…
CVE-2019-25282 — Critical (CVSS 9.8): V-SOL GPON/EPON OLT Platform v2.03 contains an open redirect vulnerability in the script that allows attackers to…
CVE-2020-36912 — Critical (CVSS 9.8): Plexus anblick Digital Signage Management 3.1.13 contains an open redirect vulnerability in the 'PantallaLogin' script…
CVE-2025-43526 — Critical (CVSS 9.8): This issue was addressed with improved URL validation. This issue is fixed in Safari 26.2, macOS Tahoe 26.2. On a Mac…
CVE-2025-55031 — Critical (CVSS 9.8): Malicious pages could use Firefox for iOS to pass FIDO: links to the OS and trigger the hybrid passkey transport. An…
CVE-2024-22891 — Critical (CVSS 9.8): Nteract v.0.28.0 was discovered to contain a remote code execution (RCE) vulnerability via the Markdown link.

Browse all CWE-601 (Open Redirect) vulnerabilities →