PatchSiren cyber security CVE debrief
CVE-2026-48845 Roundcube CVE debrief
A vulnerability in Roundcube Webmail allows remote image blocking bypass for local/private destinations, potentially enabling information disclosure or privilege escalation via crafted text/html email messages. The issue affects versions 1.6.14 through 1.6.16 in the 1.6.x branch and versions prior to 1.7.1 in the 1.7.x branch. The flaw occurs because the application's remote image blocking mechanism fails to properly restrict URLs pointing to local or private network destinations, which could allow an attacker to trigger requests to internal resources when a user views a malicious email.
- Vendor
- Roundcube
- Product
- Webmail
- CVSS
- MEDIUM 6.5
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-05-25
- Original CVE updated
- 2026-05-26
- Advisory published
- 2026-05-25
- Advisory updated
- 2026-05-26
Who should care
Organizations running Roundcube Webmail versions 1.6.14-1.6.16 or 1.7.x before 1.7.1; security teams responsible for email gateway and webmail security; administrators of environments where Roundcube has access to internal network resources or services.
Technical summary
The vulnerability stems from improper handling of URL destinations in the remote image blocking feature (CWE-669: Incorrect Resource Transfer Between Spheres). When processing text/html email messages, Roundcube Webmail fails to validate that image URLs are restricted to external/remote destinations, allowing references to local or private network addresses to bypass blocking controls. This could enable Server-Side Request Forgery (SSRF)-like behavior where viewing an email triggers unintended requests to internal services, potentially exposing sensitive information or facilitating privilege escalation in environments where internal services rely on network-based authentication or expose administrative interfaces.
Defensive priority
medium
Recommended defensive actions
- Upgrade Roundcube Webmail to version 1.6.16 or later for the 1.6.x branch, or version 1.7.1 or later for the 1.7.x branch
- Review email filtering policies to detect and quarantine suspicious HTML emails containing embedded local/private network references
- Monitor webmail access logs for unusual internal network requests originating from the webmail application
- Verify that remote image blocking settings are properly configured after patching
- Consider network segmentation to limit exposure of internal services to the webmail server
Evidence notes
Vulnerability description sourced from official CVE record and NVD entry. Affected version ranges confirmed through release tags and security advisory. Vendor identification based on reference domain evidence with low confidence requiring review.
Official resources
2026-05-25