Office CVE-2025-62554 Type Confusion: RCE Risk, MSRC Guidance, and Quick Mitigations

Microsoft’s security telemetry just added another Office advisory to the pile: CVE-2025-62554, a type‑confusion vulnerability in Microsoft Office that vendors classify as a Remote Code Execution (RCE) risk and that — based on current public records — appears to allow code execution in the context of the affected process.

Background / Overview​

Type‑confusion bugs occur when a program treats a piece of data as one type while it actually has a different internal representation. In native code — particularly long‑running, feature‑dense applications like Microsoft Office — that mismatch can corrupt memory, clobber pointers or vtables, and ultimately enable attackers to divert control flow. This class of defect is cataloged as CWE‑843 and has produced high‑impact Office advisories across 2024–2025. Independent trackers and vendor feeds have repeatedly flagged type‑confusion Office flaws as high‑risk because they frequently lead to full RCE in the user context. What the early public records show for CVE‑2025‑62554

• Short description (public): “Access of resource using incompatible type (‘type confusion’) in Microsoft Office allows an unauthorized attacker to execute code locally.”
• Scoring snapshot (published trackers): CVSS v3.1 base score reported around 8.4 (High) with a vector string entry present in public aggregators. That vector, as posted to public feeds, is listed as AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H, although the available aggregator entries are sparse on per‑SKU or KB mappings.

Important caveat: the Microsoft Security Response Center (MSRC) is the authoritative source for the CVE → KB mapping and remediation packages, but the MSRC advisory interface is dynamically rendered and requires interactive inspection to see the per‑product KB numbers and precise vendor text. Public aggregator pages link to MSRC but — at the time of writing — some MSRC pages only surface behind JavaScript and therefore require a human reviewer to confirm the vendor’s exact wording and the affected builds. Treat the vendor page as the final authority when staging patches.

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How type‑confusion in Office becomes remote code execution​

What "type confusion" means in practice​

A type‑confusion bug typically arises when a parser or runtime assumes an object or data record follows a particular layout and then acts on fields that are actually different types or lengths. In C/C++ code paths this can let attackers:

• Overwrite function pointers or vtables.
• Corrupt heap metadata and achieve write‑where primitives.
• Redirect execution into attacker‑supplied payloads.

Because Office implements complex parsers for many legacy and modern formats (OLE, BIFF, RTF, compressed XML containers, embedded objects), small mismatches in object handling can cascade into memory corruption that an exploit author can weaponize. Recent Office advisories in 2025 repeatedly show the same exploitation pattern.

Attack surface and delivery vectors​

Office RCEs can be delivered and triggered in several common ways:

• A user opens a crafted document attachment (email, chat, cloud share).
• A preview or thumbnailer automatically parses a file (Outlook preview, Explorer thumbnail).
• A server‑side renderer or document conversion service parses uploaded content (webmail, CMS previewing) — in these cases the vulnerability can be triggered without human interaction, turning a local‑vector flaw into an effective network‑accessible risk.

The publicly posted vector string for CVE‑2025‑62554 (AV:L/AC:L/PR:N/UI:N/S:U/…) — if correct — implies the vulnerability is triggered in a local process context (AV:L) and, unusually, that no user interaction is required (UI:N). That particular combination is worth scrutinizing because it changes operational priorities: a UI:N flag often indicates server‑side parsing or an automatic preview pipeline that can be abused by simply uploading a crafted file. However, public aggregator records sometimes contain metadata inconsistencies; assertive operational decisions must therefore be anchored to the MSRC advisory and per‑SKU KBs.

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Technical verification: what is confirmed and what is provisional​

• Confirmed (publicly posted, vendor‑linked):
• The CVE identifier CVE‑2025‑62554 is recorded by public CVE aggregators with the description categorizing it as a type‑confusion in Microsoft Office that can lead to code execution. Aggregators link to MSRC for vendor confirmation.
• Corroborated by other trackers and historical pattern:
• Multiple 2025 Office advisories with type‑confusion or memory corruption root causes follow the same exploit model and remediation workflow (per‑SKU KBs, multiple packaging models). Those prior advisories provide technical analogues that inform likely exploitation mechanics and mitigations. Use these patterns as operational guidance while vendor specifics are confirmed.
• Unverified / time‑sensitive claims that need vendor confirmation:
• The exact Office components, affected builds (e.g., Microsoft 365 Apps, Office LTSC, Office for Android/iOS/macOS), and the specific KB numbers that remediate CVE‑2025‑62554 are not reliably extractable from the dynamic MSRC page without human inspection. Any claim about precise KBs, exploit proofs‑of‑concept (PoCs), or in‑the‑wild exploitation should be flagged as provisional unless confirmed by MSRC, NVD, or a trusted vendor/industry advisory.

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Impact analysis — who should worry most​

• High‑value endpoints: finance, HR, legal, and any workstation that opens external spreadsheets or shared documents frequently — these are standard primary targets because spreadsheets commonly contain sensitive data and are exchanged widely.
• Mail and gateway infrastructure: mail servers and gateways that perform server‑side previewing or content scanning are priority‑one assets because an unauthenticated upload could be rendered and parsed server‑side (turning AV:L into a practical AV:N scenario).
• Cloud collaboration services and CMS that accept user uploads and render thumbnails or previews automatically. These services should be inventoried and patched quickly if they use vulnerable Office rendering components.

Practical exploitation consequences (if the public description is accurate):

• Arbitrary code execution within the Office process context (user privileges).
• Possible escalation or lateral movement if paired with credential theft or privilege‑elevation bugs.
• Data exfiltration or ransomware deployment as common follow‑on objectives.

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Mitigations and tactical controls (immediate to short term)​

Applying vendor updates is the definitive remedy, but while teams verify and schedule patches, tiered compensations are needed.
High‑priority (apply immediately)

• Install Microsoft’s security updates that map to CVE‑2025‑62554 for every Office channel in your estate (Microsoft Update, WSUS, Intune/MECM, Click‑to‑Run, or app‑store updates for mobile/mac builds). Confirm KB numbers in MSRC before deploying.
• For mail and public services, patch servers that accept uploads or perform document previews first. These servers present the greatest blast radius because they may be triggered by unauthenticated uploads.

Compensating controls (short term)

• Disable Outlook and Explorer preview panes and thumbnail generation for user groups or servers that cannot be patched immediately. Preview handlers commonly invoke the same parsing code paths exploited by Office RCEs.
• Enforce Protected View for files from the Internet and untrusted sources so documents open in a sandboxed, read‑only environment until users explicitly trust them.
• Restrict macro execution: block unsigned macros and enforce application control (AppLocker/WDAC) and Attack Surface Reduction (ASR) rules to prevent Office processes from spawning child shells or scripting engines.
• Route inbound documents through a mail gateway sandbox/detonation chamber where attachments are opened in isolated VMs and scanned before delivery.

Detection and response tuning

• Alert on Office processes (WINWORD.EXE, EXCEL.EXE, POWERPNT.EXE) spawning unexpected child processes such as cmd.exe or powershell.exe.
• Monitor for anomalous outbound connections immediately following Office file opens.
• Collect and preserve forensic artifacts (EDR snapshots, crash dumps, original malicious file) if exploitation is suspected.

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Operational checklist for IT teams (sequence and priorities)​

• Inventory: map Office install types and update channels (Click‑to‑Run vs MSI vs LTSC vs mobile). Confirm which endpoints run Microsoft 365 Apps, Office LTSC, Office for Mac, and mobile Office clients.
• Vendor verification: open the MSRC advisory for CVE‑2025‑62554 and record the per‑SKU KB numbers and package names. If the MSRC page is dynamically rendered, perform the check via a browser to retrieve the KBs.
• Patch servers first: prioritize mail gateways, Exchange servers, Office Online Server, and any public upload processors. These present the largest external risk if they parse content automatically.
• Stage to test ring: deploy to a small set of endpoints, validate application functionality, then roll out broadly.
• Apply compensations while staging: disable previews, enable Protected View, and enforce macro policy.
• Validate: confirm KBs are installed (via Intune/SCCM/MECM or Microsoft Update logs) and that build numbers match the vendor advisory before declaring systems remediated.

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Confidence, evidence, and the "report confidence" metric​

The user‑supplied metric in the MSRC advisory ecosystem — sometimes labeled “report confidence” or similar — grades how certain Microsoft is about the vulnerability description and the correctness of the remediation mapping. For defenders that metric is operationally useful: a vendor‑confirmed CVE with high confidence and a released KB should be treated as actionable. When the advisory is corroborated by independent researchers or vendors, that increases confidence further. Conversely, if only a CVE string exists without per‑SKU KBs or vendor confirmation, treat technical details as provisional and prioritize vendor verification before rolling changes.
At present, public aggregators record CVE‑2025‑62554 and classify it as type‑confusion RCE; however, because MSRC pages are the canonical record for patch mapping and the dynamic rendering can obscure details to automated scrapers, defenders should always validate the KB numbers and the exact affected products directly on MSRC before deploying. If you automate patch acceptance purely on third‑party aggregator input, you risk installing the wrong package for a given install model.

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Strengths of the public advisory posture — and the risks​

Strengths

• Vendor release of a CVE identifier focuses attention and enables rapid triage. Public tracking aggregates (vulnerability databases, CERTs, vendor blogs) help security teams prioritize and plan mitigations.
• The known mitigation set for Office RCEs (patch, Protected View, disable preview panes, ASR rules) is well‑established and effective at reducing immediate exposure while teams patch.

Risks and limitations

• Metadata inconsistencies across public aggregators (CVSS vectors, UI flags) can cause confusion: for example, a CVSS UI:N claim combined with an AV:L designation requires careful interpretation because it implies automatic parsing (server‑side or preview) rather than manual open. If you assume one interpretation without verifying the advisory body, you risk misprioritizing assets.
• MSRC’s dynamic UI and per‑SKU KB fragmentation mean that patch teams must map CVE → KB → build carefully; a single Windows Update package does not necessarily fix all Office packaging models. Missing that nuance is a common operational error.
• Public PoCs or exploit chatter can appear quickly once an advisory and patch are public. Historically, motivated attackers analyze patches to reverse‑engineer flaws and produce weaponized exploits; this accelerates after vendor disclosure. Prioritize remediation for the highest‑exposure assets immediately.

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Verified cross‑checks performed for this analysis​

• CVE aggregator listing: CVE‑2025‑62554 recorded on public aggregator sites with a short description and posted CVSS vector.
• Historical pattern and mitigation guidance: consolidated vendor and third‑party guidance for Office RCE advisories in 2024–2025 (type confusion, heap overflows, out‑of‑bounds reads) used to derive practical mitigations and triage steps. These corroborating patterns come from multiple independent trackers and vendor update notes.

Flagged items that require a follow‑up verification:

• Per‑SKU KB numbers and patched build numbers for all Office channels must be retrieved directly from the MSRC Update Guide (open via a browser to ensure the JavaScript‑rendered content is visible) before deploying updates.
• Any assertion that exploitation is observed in the wild or that a public PoC exists should be re‑checked against telemetry and vendor/national CERT advisories at the time of triage; those are highly time‑sensitive facts.

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Actionable summary — immediate to 72‑hour plan​

• Confirm: open the MSRC advisory for CVE‑2025‑62554 in a browser and record the KB(s) that Microsoft lists for each Office channel and platform. Do not rely solely on third‑party aggregators for KB mapping.
• Patch: prioritize servers and services that parse user uploads (mail gateways, Office Online Server, CMS) and apply vendor updates immediately.
• Compensate: disable Outlook/Explorer preview panes, enable Protected View for internet files, enforce macro restrictions, and apply ASR/AppLocker rules where feasible.
• Detect and contain: tune EDR to alert on Office‑spawned child processes and anomalous network activity; isolate and preserve evidence if exploitation is suspected.
• Validate: confirm KB installation by build number in your patch management console before closing the remediation ticket.

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Conclusion​

CVE‑2025‑62554 is categorized in public feeds as a type‑confusion RCE in Microsoft Office and should be treated as a high priority for defenders, particularly those responsible for mail gateways, server‑side renderers, and any environment that automatically parses user‑supplied documents. Aggregator records show a high CVSS rating and a type‑confusion root cause, but the definitive operational details — per‑SKU KBs, exact affected builds, and MSRC’s advisory text — must be verified on Microsoft’s Security Update Guide before mass deployment.
Apply the standard, proven mitigations now: patch servers first, enforce Protected View, disable previews, lock down macros, and tune EDR detections. Flag any low‑level exploit claims or reports of in‑the‑wild use as provisional until MSRC, NVD, or multiple trusted vendors corroborate them. The combination of vendor confirmation and rapid patch deployment remains the single most effective defense against Office document RCEs.

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Source: MSRC Security Update Guide - Microsoft Security Response Center