RomCom hackers chained Firefox and Windows zero-days to deliver backdoor

CVE-2023-36884 is a race condition (TOCTOU) vulnerability in Microsoft Windows Search that permits remote code execution, rated 7.5 (high) on CVSS 3.1. It is triggered over the network with user interaction — for example, when a user opens or interacts with a specially crafted document that causes the vulnerable search code path to race, allowing arbitrary code execution in the context of the current user. An attacker gains code execution on the victim's Windows system, which the RomCom threat actor chained with Firefox flaws to deploy backdoors against political targets, and CISA notes known ransomware use. Virtually every supported Windows client and server release at the time is affected, spanning Windows 10 1507 through 22H2, Windows 11 21H2/22H2, and Windows Server 2008 through 2022. The flaw was actively exploited as a zero-day before being fixed in the July 2023 Patch Tuesday; it was added to the CISA KEV catalog on 2023-07-17 and carries a 98.9% EPSS score (100th percentile).

Do: Apply the July 2023 Patch Tuesday Windows security updates to all Windows 10, Windows 11, and Windows Server systems, prioritizing high-value and frequently attacked endpoints since the bug was exploited as a zero-day by RomCom and carries a KEV deadline (US civilian agencies were directed to remediate by August 1, 2023). Because exploitation requires user interaction, caution users against opening untrusted documents, and verify patch status via your patch management or vulnerability scanner against the KEV requirement. If patching is not possible, follow vendor mitigations per CISA's required action or discontinue use.

CVE-2024-49039 is an elevation-of-privilege vulnerability (CWE-287, improper authentication) in the Microsoft Windows Task Scheduler, scored 8.8 (High) with a local attack vector, low required privileges, and a changed scope indicating the exploit crosses a security boundary. A local attacker with limited user privileges can trigger the flaw through Task Scheduler to gain elevated rights on the affected system, typically SYSTEM- or administrator-level control, with no user interaction required. Every supported Windows desktop and server release in the vendor's affected list is impacted, since Task Scheduler is a core component of the operating system. The flaw was patched as an actively exploited zero-day in the November 2024 Patch Tuesday release, was added to CISA's Known Exploited Vulnerabilities catalog on 2024-11-12, and ransomware operators are known to use it. With an EPSS of 14.2% (96th percentile), defenders should treat this as a high-priority local privilege escalation for privilege-chaining and ransomware campaigns.

Do: Apply the November 2024 Windows security updates across all affected Windows 10, Windows 11, and Windows Server branches, prioritizing servers, jump hosts, and machines used by privileged users given confirmed ransomware use. Confirm no supported Windows host is left unpatched, review local task creation and authentication logs for signs of privilege escalation, and follow CISA's required action to apply vendor mitigations or discontinue use if patches are unavailable.

Mozilla Firefox and Firefox ESR contain a use-after-free (CWE-416) in the browser's animation timelines component, which CISA describes as allowing code execution in the content process. The flaw is reachable through malicious web content: a crafted page can manipulate animation timelines so that an in-use object is freed, producing exploitable memory corruption. A successful attacker gains code execution in the content process, the sandboxed process that renders web pages, on the machine of the user who loaded the content. All users of Firefox and Firefox ESR are affected by the flaw itself. It is being actively exploited: the vulnerability was added to CISA's Known Exploited Vulnerabilities catalog on 2024-10-15 with known ransomware use, and EPSS assigns it a 23.2% probability of exploitation in the next 30 days (98th percentile).

Do: Apply Mozilla's patched Firefox/Firefox ESR release immediately and verify the running version via the browser's About Firefox dialog, since many installs only pick up auto-updates after a restart (per CISA's required action: apply mitigations per vendor instructions or discontinue use). Given the known ransomware use, prioritize enterprise ESR rollout and check for managed-update failures, auto-update-disabled installs, or unmanaged Firefox copies on user machines. Note that no public proof-of-concept is known, but KEV listing confirms exploitation, so patching should not wait for PoC availability.