CVE-2026-35542 Roundcube CVE debrief

Who should care

Users of Roundcube Webmail versions before 1.5.14 and 1.6.14 should apply patches to prevent potential information disclosure or access-control bypass. This vulnerability may impact organizations using affected versions of Roundcube Webmail, particularly those with high security requirements. Operators, platform administrators, and security teams should review the vulnerability and apply mitigations as necessary.

Technical summary

The vulnerability exists in Roundcube Webmail before versions 1.5.14 and 1.6.14. An attacker can bypass the remote image blocking feature by crafting a specific background attribute in an email message. This could potentially lead to information disclosure or access-control bypass. The CVSS score for this vulnerability is 5.3, indicating a medium severity level. The vulnerability can be mitigated by applying patches from Roundcube Webmail versions 1.5.14 and 1.6.14.

Defensive priority

Apply patches to prevent potential information disclosure or access-control bypass in Roundcube Webmail. Review email content handling and filtering mechanisms. Monitor for suspicious email activity.

Recommended defensive actions

• Apply patches from Roundcube Webmail versions 1.5.14 and 1.6.14.
• Review email content handling and filtering mechanisms.
• Monitor for suspicious email activity.
• Update to version 1.7-rc5 or later if available.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.

Evidence notes

The CVE record was published on 2026-04-03T05:16:22.460Z and was last modified on 2026-07-24T21:10:00.143Z. The NVD entry is currently Analyzed. This information is based on the NVD entry and the CVE record. The remote image blocking feature bypass in Roundcube Webmail can be exploited via a crafted background attribute in an email message, potentially leading to information disclosure or access-control bypass. Evidence is limited to public sources and may not reflect the full scope or impact of the vulnerability.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.