Roundcube webmail XSS vulnerability exploited by attackers (CVE-2023-43770)

Roundcube Webmail contains a cross-site scripting (XSS) flaw (CWE-79) in the link-reference handling of rcube_string_replacer.php, where the linkref_addindex function mishandles JavaScript embedded in a link element of a plain-text email. An attacker triggers the flaw simply by sending a crafted plain-text message to a victim; when the message is processed/displayed in the Roundcube interface, the embedded script executes in the context of the victim's webmail session. Successful exploitation can lead to session hijacking, theft of webmail cookies or credentials, and arbitrary actions in the victim's mailbox. Any deployment of Roundcube Webmail is affected, which includes self-hosted instances and webmail offered by hosting providers, ISPs, and universities. Although no public proof-of-concept is known, CISA added this vulnerability to the Known Exploited Vulnerabilities catalog on 2023-06-22, confirming exploitation in the wild; ransomware association is unknown, and no CVSS score is yet available, though EPSS puts 30-day exploitation probability at 32.7% (98th percentile).

Do: Apply the vendor's updated Roundcube release per CISA's required action (updates per vendor instructions); since no specific fixed versions appear in this data, install the latest patched release of your deployed 1.x branch and verify with the vendor advisory. Check webmail servers for processing of plain-text messages with link-reference elements and review logs for anomalous webmail sessions; treat KEV-listed status as evidence of active exploitation and prioritize internet-exposed Roundcube instances.

Roundcube Webmail contains a SQL injection flaw (CWE-89) in which attacker-controlled 'search' or 'search_params' input is incorporated into database queries without sufficient sanitization. An attacker with access to the webmail search functionality (typically an authenticated mailbox user) can submit crafted parameters to execute arbitrary SQL against the Roundcube backend database, potentially reading or modifying stored mail account data. Any organization running Roundcube is affected, including self-hosted mail servers and customers of hosting providers that ship Roundcube as their bundled webmail client. The flaw was added to CISA's Known Exploited Vulnerabilities catalog on 2023-06-22, indicating exploitation in the wild, and EPSS assigns a 41.9% probability of exploitation within 30 days (99th percentile). No public proof-of-concept is known, and CISA lists ransomware use as unknown.

Do: Apply vendor updates per Roundcube's instructions by upgrading to the latest patched, supported release, prioritizing internet-facing webmail servers; federal agencies must remediate per the CISA KEV requirement. If Roundcube is managed by a hosting provider (e.g., via cPanel), coordinate patching with them. In the interim, restrict webmail exposure and review database and web logs for anomalous search-related queries that may indicate exploitation.

Roundcube Webmail versions before 1.4.14, 1.5.x before 1.5.4, and 1.6.x before 1.6.3 contain a persistent cross-site scripting (XSS) flaw (CWE-79) caused by how program/lib/Roundcube/rcube_string_replacer.php converts plain text into clickable links. An attacker sends a text/plain email containing crafted links; when the recipient views the message, the crafted link text is turned into HTML that runs attacker-controlled script, which persists and executes in the victim's webmail session. Successful exploitation lets the attacker execute JavaScript with the victim's session, enabling mailbox access, theft of session credentials, and actions performed as the user (CVSS 6.1, scope-changed with limited confidentiality and integrity impact). Anyone running an affected Roundcube instance is exposed, including the roundcube package shipped with Debian Linux. The flaw is being actively exploited: CISA added it to the Known Exploited Vulnerabilities catalog on 2024-02-12, and EPSS assigns a 58.5% probability of exploitation within 30 days (99th percentile).

Do: Upgrade Roundcube to 1.4.14, 1.5.4, or 1.6.3 (or later, per branch), or install the updated roundcube package on Debian. Because the bug is in CISA's KEV catalog, U.S. federal agencies must apply the vendor fix by the catalog due date, and other defenders should prioritize patching internet-facing webmail servers. Review webmail access logs for suspicious message views or account activity, and consider forcing session re-authentication for accounts that opened crafted plain-text messages.