What happened

CISA added CVE-2011-3402 to the Known Exploited Vulnerabilities (KEV) catalog on 2025-10-06, establishing a remediation due date of 2025-10-27 for covered entities CISA KEV. The entry tracks a Windows kernel remote code execution vulnerability in the TrueType font parsing engine within win32k.sys NVD entry. The issue is explicitly described as an unspecified flaw that permits RCE when a target processes crafted font data embedded in a Microsoft Word document or rendered from a web page NVD entry, with the canonical CVE metadata aligned at MITRE MITRE CVE record.

Why it matters

KEV listing means exploitation has been observed in the wild and agencies are directed to remediate on deadline CISA KEV. This vulnerability lives in the Windows kernel’s font parsing path (win32k.sys), which processes TrueType data supplied by untrusted content, making it a high-impact pre-execution vector through routine user actions like opening a document or visiting a site NVD entry. Because the flaw enables arbitrary code execution via crafted fonts in Word docs or web pages, it compresses the kill chain: no macros, no special privileges—just rendering content can be enough NVD entry. For environments where Windows hosts still encounter legacy documents or untrusted web content, this path is both common and operationally hard to fully eliminate MITRE CVE record.

Technical detail

Per the CVE, the vulnerability is an unspecified error in the TrueType font parsing engine within the kernel-mode win32k.sys driver NVD entry. The trigger condition is the handling of maliciously crafted font data—specifically TrueType—embedded in content streams that Windows will parse during normal rendering NVD entry. Two primary delivery channels are documented: Microsoft Word documents that include the crafted font payload and web pages that cause the vulnerable code paths to engage when the browser renders text NVD entry. The outcome cited is remote code execution, reflecting the ability of an attacker to run arbitrary code on the victim machine once the vulnerable font parser is invoked MITRE CVE record. Because the affected component resides in a kernel-mode driver, exploitation impacts a highly privileged execution surface that underpins the Windows GUI and text rendering stack NVD entry.

From an exploitation standpoint, the attacker’s prerequisite is to deliver content that will be parsed by the TrueType engine, which includes document workflows and web browsing paths documented in the CVE NVD entry. The KEV inclusion signals that adversaries have operationalized this vector, and CISA’s directive sets a clear timeline for remediation CISA KEV. MITRE’s record mirrors the NVD description, reinforcing the remote code execution characteristics tied to crafted TrueType data in win32k.sys MITRE CVE record.

Defense

CISA’s required action for KEV entries is to apply mitigations per vendor guidance, follow applicable BOD 22-01 processes for cloud and enterprise service enforcement, or discontinue use where mitigations are not available CISA KEV. Prioritize Windows assets that routinely process untrusted documents and browse external sites, since these are the explicitly documented vectors for this CVE NVD entry. Validate that patch management and configuration baselines close the TrueType font parsing pathway that is exploited by malicious Word documents and web pages NVD entry. For risk reduction while patching, restrict exposure to untrusted documents and external web content on high-value Windows hosts, aligning control focus to the content-rendering vectors described in the CVE entry MITRE CVE record.

Operational steps:

• Inventory Windows endpoints and servers that handle external documents or web traffic; these are the documented trigger paths for this RCE NVD entry.
• Accelerate patch SLAs for mission-critical systems per CISA KEV deadlines and governance CISA KEV.
• Tighten content ingress for email and web where feasible, reducing rendering of untrusted fonts consistent with the CVE’s vectors NVD entry.

Lyrie Verdict

Font-parsing RCEs delivered through everyday content flows are exactly where autonomous threats thrive: low-friction delivery and deterministic triggers via Word or web rendering NVD entry. Lyrie’s stance is to detect and contain at machine speed at the moment untrusted content execution paths engage the vulnerable font parser documented in CVE-2011-3402 MITRE CVE record. Concretely, we bind autonomous policies to document and browser workloads and escalate protection whenever Windows attempts to parse TrueType data from untrusted sources, the exact delivery mechanism cited by the CVE and enforced by KEV remediation priority CISA KEV.