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Vulnerability record · CVE-2026-53727 · published 17 July 2026

CVE-2026-53727: Premailer css parser server-side request forgery (ssrf) vulnerability

Premailer · Css Parser

css_parser is a Ruby CSS parser. From 2.2.0 until 3.0.0, CssParser::Parser#read_remote_file in lib/css_parser/parser.rb, and therefore load_uri! and the @import-following branch of add_block!, issued HTTP and HTTPS requests against any host, port, and URI without a scheme allowlist, host or IP filtering, or protection against link-local, loopback, or RFC-1918 addresses. Location: redirects were followed recursively back into the same function, which also serviced file:// URIs, so a single attacker-controlled HTTP redirect could upgrade the bug from SSRF to arbitrary local file disclosure. Any consumer of css_parser that hands it attacker-influenced CSS together with a base_uri: option is exposed. This issue is fixed in version 3.0.0.

8.9 CVSS 4.0 High EPSS 0.51% · top 59.2% CWE-918 · Server-side request forgery (SSRF)
8.9CVSS 4.0 base score
0.51%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
5References, 2 tagged exploit
18 Aug 2026Last modified by NVD

Description

css_parser is a Ruby CSS parser. From 2.2.0 until 3.0.0, CssParser::Parser#read_remote_file in lib/css_parser/parser.rb, and therefore load_uri! and the @import-following branch of add_block!, issued HTTP and HTTPS requests against any host, port, and URI without a scheme allowlist, host or IP filtering, or protection against link-local, loopback, or RFC-1918 addresses. Location: redirects were followed recursively back into the same function, which also serviced file:// URIs, so a single attacker-controlled HTTP redirect could upgrade the bug from SSRF to arbitrary local file disclosure. Any consumer of css_parser that hands it attacker-influenced CSS together with a base_uri: option is exposed. This issue is fixed in version 3.0.0.

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/premailer/css_parser/commit/7d2ddf0189cd54b54f378f59daefa10cb036e476 Patch
https://github.com/premailer/css_parser/commit/e0a151458b2a801ae265ba420862ef8b1127b3ae Patch
https://github.com/premailer/css_parser/releases/tag/v3.0.0 Product
https://github.com/premailer/css_parser/security/advisories/GHSA-9pmc-p236-855h ExploitMitigationVendor Advisory
https://github.com/premailer/css_parser/security/advisories/GHSA-9pmc-p236-855h ExploitMitigationVendor Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-53727), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.