What is CVE-2018-19131?

CVE-2018-19131 is a medium-severity vulnerability in Squid-Cache Squid, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2018-11-09.

How severe is CVE-2018-19131?

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

Is CVE-2018-19131 known to be exploited?

5 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

XSS in Squid-Cache Squid

CVE-2018-19131

Squid before 4.4 has XSS via a crafted X.509 certificate during HTTP(S) error page generation for certificate errors.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2018-11-09 · 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: 0.033 (88.2th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 88th percentile — 88.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.033 · newest: 0.033 · change: 0.000

Affected products

Squid-Cache Squid

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

Public proof-of-concept exploits

References

www.squid-cache.org/Versions/v5/changesets/squid-5-6feeb15ff312f3e145763adf8d23… (Patch, Vendor Advisory)
www.squid-cache.org/Advisories/SQUID-2018_4.txt (Mitigation, Vendor Advisory)
github.com/squid-cache/squid/pull/306 (Third Party Advisory)

Frequently asked questions

What is CVE-2018-19131?: CVE-2018-19131 is a medium-severity vulnerability in Squid-Cache Squid, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2018-11-09.
How severe is CVE-2018-19131?: Medium severity. CVSS v3 base score is 6.1 out of 10.
Is CVE-2018-19131 known to be exploited?: 5 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.