Week in review: AnyDesk phishing campaign targets employees, Microsoft fixes exploited zero-days

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.

An OS command injection vulnerability has been reported to affect several QNAP operating system versions. If exploited, the vulnerability could allow users to execute commands via a network. We have already fixed the vulnerability in the following versions: QTS 5.1.5.2645 build 20240116 and later QuTS hero h5.1.5.2647 build 20240118 and later QuTScloud c5.1.5.2651 and later

CVE-2024-21412 is a security feature bypass (CWE-693) in how Microsoft Windows handles Internet Shortcut files: a crafted shortcut can make Windows skip the security warning prompt that normally appears before untrusted internet content is opened or downloaded. Triggering it requires user interaction — an attacker must deliver a malicious shortcut file, typically via email or a malicious website, and convince the user to open it, which is reflected in the CVSS vector's UI:R component. An attacker who succeeds gains a bypass of those prompts, making it easier to retrieve and execute malicious remote content with fewer warnings; the DarkGate malware operators used exactly this technique in zero-day campaigns to distribute their loader. Anyone running the affected Windows 10 (1809, 21H2, 22H2), Windows 11 (21H2, 22H2, 23H2), Windows Server 2019, or Windows Server 2022 (including 23H2) builds was exposed. The flaw was patched in Microsoft's February 2024 Patch Tuesday release (2024-02-13), the same day CISA added it to the KEV catalog, and it is under active exploitation with known ransomware association and a 95.4% EPSS score.

Do: Apply the February 2024 Windows cumulative security update (released 2024-02-13) or any later monthly cumulative update to every affected Windows 10, Windows 11, Windows Server 2019, and Windows Server 2022 build, and verify patch levels through your endpoint inventory. Because exploitation requires user interaction, as an interim control flag or block .url/Internet Shortcut attachments at email gateways and remind users not to open shortcuts from untrusted sources. Prioritize internet-facing and shared endpoints given the KEV listing and known ransomware use.

CVE-2024-21762 is a critical (CVSS 9.8) out-of-bounds write (CWE-787) in the SSL VPN functionality of Fortinet FortiOS and FortiProxy, allowing an unauthenticated remote attacker to execute unauthorized code or commands by sending specifically crafted requests to the vulnerable service. No authentication or user interaction is required, and network access to the SSL VPN interface is the only precondition. Organizations running affected FortiOS versions (on FortiGate appliances) or any affected FortiProxy version are exposed, particularly where the SSL VPN is internet-facing. The flaw is actively exploited: it was added to CISA's Known Exploited Vulnerabilities catalog on 2024-02-09 with ransomware use noted, EPSS puts the 30-day exploitation probability at 84.3%, and public scans suggest roughly 150,000 internet-exposed Fortinet devices may be impacted.

Do: Upgrade FortiOS and FortiProxy to fixed releases outside the affected ranges per Fortinet's advisory, prioritizing internet-facing devices; as an interim mitigation, disable SSL VPN (or SSL VPN web mode) where it is not required, per vendor and CISA guidance. After patching, check for signs of compromise and rotate credentials, since Fortinet has warned that attackers retained access to FortiGate devices post-patching. The flaw is in CISA KEV with known ransomware use, so treat this as an urgent patching priority.

CVE-2024-21893 is a server-side request forgery (SSRF) vulnerability in the SAML component of Ivanti Connect Secure (formerly Pulse Connect Secure), Ivanti Policy Secure, and Ivanti Neurons. A remote attacker can trigger the flaw with crafted unauthenticated requests to the SAML component, causing the appliance to make requests to otherwise restricted resources. Successful exploitation allows the attacker to access certain restricted resources without any credentials, and CISA notes the flaw has been used in ransomware operations. Any organization running an affected Ivanti Connect Secure, Policy Secure, or Neurons deployment is exposed, particularly where the appliance is reachable from the internet. The vulnerability is confirmed exploited in the wild: it was added to CISA's Known Exploited Vulnerabilities catalog on 2024-01-31, carries an EPSS probability of 100%, and no public proof-of-concept is known.

Do: Apply Ivanti's released patches or the vendor-issued mitigations immediately per vendor instructions, or discontinue use of the product if mitigations are unavailable, as required by CISA. Because ransomware use is documented, review SAML-related logs and appliance audit trails for signs of exploitation and follow-on compromise, and check for indicators of post-exploitation activity. Monitor Ivanti advisories for patched version numbers and updated mitigation guidance, since specific fixed versions are not yet specified in the available data.

An integer underflow vulnerability exists in the sopen_FAMOS_read functionality of The Biosig Project libbiosig 2.5.0 and Master Branch (ab0ee111). A specially crafted .famos file can lead to an out-of-bounds write which in turn can lead to arbitrary code execution. An attacker can provide a malicious file to trigger this vulnerability.