CVE-2026-35540

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{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[1.6.0,1.6.14)"}}], "enrichment": {"confidence": 90.0, "confidence_source": "inferred", "scores": [{"score": 90.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Webmail", "source": "cna", "vendor": "Roundcube"}, "product": "webmail", "vendor": "roundcube"}], "analysis": {"en": {"generated_at": "2026-04-03T07:23:37.516419+00:00", "value": {"mitigation_remediation": ["Upgrade Roundcube Webmail to version 1.6.14 or newer, or to the 1.7\u2011rc5 release which contains the CSS sanitization fix.", "Verify that the updated installation includes the patched sanitization logic by reviewing the release notes or checking for the presence of the corrected style handling code.", "Monitor email logs for anomalous external stylesheet requests or attempts to reach internal network hosts, and consider blocking external CSS links if immediate upgrade is not feasible."], "summary": {"action": "Immediate Patch", "impact": "Information Disclosure and SSRF"}, "threat_synthesis": {"affected_systems": "Roundcube Webmail versions that precede 1.6.14, specifically 1.6.0 through 1.6.13, are affected. The release 1.6.14 and later, as well as the 1.7\u2011rc5 release, contain the fix that properly sanitizes or blocks external stylesheets.", "description_and_impact": "The vulnerability originates from insufficient CSS sanitization in the rendering of HTML e\u2011mail messages. When an attacker crafts an email containing malicious <link> or style tags that point to internal network hosts, the client may fetch the resource, exposing internal addresses or allowing the attacker to verify their existence. This can lead to Server Side Request Forgery or inadvertent disclosure of local network resources.", "risk_and_exploitability": "The CVSS score of 5.4 classifies the issue as medium severity. No EPSS data is provided, and the vulnerability is not listed in CISA\u2019s KEV catalog, suggesting a lower exploitation probability. The attack requires the victim to open a crafted email or have the mail client fetch external stylesheets, indicating a user\u2011interaction or local\u2011host based vector rather than a purely remote exploit."}}}}, "created": "2026-04-03T07:31:07.654661+00:00", "title": "Roundcube Webmail CSS Sanitization Issue Allows SSRF and Information Disclosure", "updated": "2026-04-03T09:15:54.326330+00:00", "vendors": ["roundcube", "roundcube$PRODUCT$webmail"]}