What is CVE-2018-6520?

CVE-2018-6520 is a medium-severity vulnerability in Simplesamlphp, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2018-02-02.

How severe is CVE-2018-6520?

Medium severity. CVSS v3 base score is 6.1 out of 10.

Open Redirect in Simplesamlphp

CVE-2018-6520

SimpleSAMLphp before 1.15.2 allows remote attackers to bypass an open redirect protection mechanism via crafted authority data in a URL.

Vulnerability class: Open Redirect

Published 2018-02-02 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.009 (56.6th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 57th percentile — 56.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.009 · change: +0.000

Affected products

Simplesamlphp

Weakness classification (CWE)

CWE-601 — URL Redirection to Untrusted Site (Open Redirect)

References

simplesamlphp.org/security/201801-02 (Vendor Advisory)

Frequently asked questions

What is CVE-2018-6520?: CVE-2018-6520 is a medium-severity vulnerability in Simplesamlphp, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2018-02-02.
How severe is CVE-2018-6520?: Medium severity. CVSS v3 base score is 6.1 out of 10.