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.
CVE-2026-53727
HIGHPre-NVD 8.98.9—Trending — 3 sources updated this weekElevated
EchelonGraph scoreMEDIUM confidence
This high-severity CVE scores 8.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5%, top 61% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: epss, secondary
8.9
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 8.9Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 8.9
- EG Score
- 8.9(medium)
- EG Risk
- —
- EPSS
- 39.2%
- KEV
- Not listed
Published
July 9, 2026
Last Modified
July 20, 2026
Advisory Details (3)
Auto-updated Jul 17, 2026🔬 Proof of concept available. Patch available. Sources: github_commit, github.
github Patch Available🟡 PoC Available
SSRF and Local File Disclosure in `CssParser::Parser#read_remote_file` · Advisory · premailer/css_parser · GitHub
https://github.com/premailer/css_parser/security/advisories/GHSA-9pmc-p236-855hgithub_commit
commit e0a151458b2a (premailer/css_parser)
Fix landed in premailer/css_parser commit e0a151458b2a — awaiting tagged release
https://github.com/premailer/css_parser/commit/e0a151458b2a801ae265ba420862ef8b1127b3aegithub_commit
commit 7d2ddf0189cd (premailer/css_parser)
Fix landed in premailer/css_parser commit 7d2ddf0189cd — awaiting tagged release
https://github.com/premailer/css_parser/commit/7d2ddf0189cd54b54f378f59daefa10cb036e476Vendor Advisories for CVE-2026-53727(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Affected Packages
(1 across 1 ecosystem)
RubyGems(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| css_parser | 0.9.0 ... 2.2.0 (64 versions) | 3.0.0 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 9× in last 7d / 10× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-22 14:08 UTCEPSS rescore
- 2026-07-21 15:25 UTCEPSS rescore
- 2026-07-20 17:08 UTCEPSS rescore
- 2026-07-19 14:31 UTCEPSS rescore
- 2026-07-19 14:31 UTCEPSS rescore
- 2026-07-19 03:42 UTCEG score recompute
- 2026-07-19 02:29 UTCEPSS rescore
- 2026-07-17 20:35 UTCEG score recompute▲ 8.90
- 2026-07-17 20:34 UTCMITRE cvelistV5CVSS v3 → 8.9 · CVSS v4 → 8.9
- 2026-07-09 13:45 UTCEG score recompute
Related CVEs(same CWE)
Same CWE
10 shownCWE-918
Frequently asked(5)
What is CVE-2026-53727?
CVE-2026-53727 is a high vulnerability published on July 9, 2026. cssparser is a Ruby CSS parser. From 2.2.0 until 3.0.0, CssParser::Parser#readremotefile in lib/cssparser/parser.rb, and therefore loaduri! and the @import-following branch of addblock!, issued HTTP and HTTPS requests against any host, port, and URI without a scheme allowlist, host or IP filtering,…
When was CVE-2026-53727 disclosed?
CVE-2026-53727 was first published in the National Vulnerability Database on July 9, 2026, with the most recent update on July 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-53727 actively exploited?
CVE-2026-53727 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 39.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-53727?
CVE-2026-53727 has a CVSS v3 base score of 8.9 (NVD).
How do I remediate CVE-2026-53727?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-53727, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-53727
Is Your Infrastructure Affected by CVE-2026-53727?
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