Microsoft’s Security Update Guide lists CVE-2025-53736 as a Microsoft Word information-disclosure vulnerability caused by a buffer over-read in Word that can allow an unauthorized local actor to read memory and disclose sensitive information on a victim machine; administrators are strongly advised to treat this class of bug as high priority and to apply Microsoft’s supplied updates immediately. (msrc.microsoft.com)
Memory-safety bugs — including buffer over-reads — remain one of the most persistent attack surfaces across desktop productivity software. A buffer over-read occurs when code reads past the end of an allocated buffer and returns data that was not intended for the caller. That leaked memory can contain secrets, credentials, pointers that defeat mitigations (like ASLR), or other sensitive artifacts useful for follow‑on attacks. Public trackers and vendor advisories consistently classify buffer over-read issues as information disclosure (CWE-126/CWE-125) when the primary consequence is data leakage rather than immediate code execution. (nvd.nist.gov)
Microsoft Word has historically been targeted by attackers because of its ubiquity, complex parsing code paths (file formats, embedded objects, preview/thumbnail handlers), and the variety of ways a document can be delivered and rendered (email attachments, file shares, cloud storage, preview panes). In recent Patch Tuesday cycles vendors fixed multiple Word and Office parsing bugs that either allowed code execution or, as with information disclosure flaws, could leak memory contents when a specially crafted file is processed or previewed. Enterprise Patch Tuesday write-ups from July 2025 show Word and Office as recurring flashpoints in Microsoft’s monthly updates.
Caveat — current verifiability: the MSRC entry you provided lists the vulnerability; however, at the time of reporting the CVE did not appear to be broadly indexed in every public tracker searched during research. That means independent public write‑ups or third‑party technical breakdowns for CVE‑2025‑53736 were not available for cross‑reference; treat vendor guidance as primary source until independent technical reports are published. (msrc.microsoft.com)
End of report.
Source: MSRC Security Update Guide - Microsoft Security Response Center
Memory-safety bugs — including buffer over-reads — remain one of the most persistent attack surfaces across desktop productivity software. A buffer over-read occurs when code reads past the end of an allocated buffer and returns data that was not intended for the caller. That leaked memory can contain secrets, credentials, pointers that defeat mitigations (like ASLR), or other sensitive artifacts useful for follow‑on attacks. Public trackers and vendor advisories consistently classify buffer over-read issues as information disclosure (CWE-126/CWE-125) when the primary consequence is data leakage rather than immediate code execution. (nvd.nist.gov)Microsoft Word has historically been targeted by attackers because of its ubiquity, complex parsing code paths (file formats, embedded objects, preview/thumbnail handlers), and the variety of ways a document can be delivered and rendered (email attachments, file shares, cloud storage, preview panes). In recent Patch Tuesday cycles vendors fixed multiple Word and Office parsing bugs that either allowed code execution or, as with information disclosure flaws, could leak memory contents when a specially crafted file is processed or previewed. Enterprise Patch Tuesday write-ups from July 2025 show Word and Office as recurring flashpoints in Microsoft’s monthly updates.
What the advisory says (summary)
- The entry in Microsoft’s Security Update Guide identifies CVE-2025-53736 as an information disclosure vulnerability in Microsoft Word. The root cause is a buffer over-read in a Word component that can return memory to an attacker under certain local conditions. (msrc.microsoft.com)
- Microsoft’s public advisory text for similar Office CVEs emphasizes that these bugs often require local access or user interaction (for example, opening a malicious file or viewing it in the Preview Pane), which constrains remote mass exploitation but does not eliminate serious risk in real-world environments where attackers can lure users to open documents.
Technical analysis: how a buffer over-read in Word can be abused
What a buffer over-read actually does
A buffer over-read happens when parsing routines assume a size or count that is larger than what the input provides, then read memory beyond the intended bounds. Unlike overflows that may allow code injection, over-reads typically leak data (heap contents, stack data, pointers) back to the caller or into a response. That data is valuable to attackers because:- It may include tokens, passwords, or parts of files loaded in memory.
- It can expose memory addresses that defeat Address Space Layout Randomization (ASLR), making subsequent exploitation of unrelated bugs much easier.
- Even small leaks can be chained into larger compromises when paired with other flaws or social-engineered access.
How Word’s architecture amplifies risk
Word parses a range of complex content: RTF, DOC/DOCX internals, embedded OLE objects, images, fonts and fonts descriptors, and hyperlink/metadata handlers. Many of these parsers run in-process with Word (or in the preview handlers used by Explorer/Outlook), and when a malformed document reaches those parsers the result can be anything from a crash to a silent leak of memory. The Preview Pane/preview handlers increase the attack surface because rendering may happen without explicit user interaction beyond selecting a message or file. Published Patch-Tuesday reports highlight Preview Pane exposures as a recurring theme.Exploitation scenarios (realistic threat models)
- A phishing email carries a crafted document. A user opens or previews it in Outlook/Explorer; Word’s parser performs an out-of-bounds read and leaks parts of process memory (possibly to be exfiltrated via a second stage).
- A local attacker with limited privileges (low‑privilege account on a shared workstation or in a multi‑user desktop/VDI environment) crafts a document or places it on a shared folder, causing Word to read and reveal memory contents accessible to the attacker.
How severe is CVE-2025-53736?
Severity depends on:- What memory is leaked (secrets vs. benign data).
- Whether user interaction or local access is required.
- Whether leaked content can be used to escalate privileges or enable remote exploitation of other flaws.
Caveat — current verifiability: the MSRC entry you provided lists the vulnerability; however, at the time of reporting the CVE did not appear to be broadly indexed in every public tracker searched during research. That means independent public write‑ups or third‑party technical breakdowns for CVE‑2025‑53736 were not available for cross‑reference; treat vendor guidance as primary source until independent technical reports are published. (msrc.microsoft.com)
Immediate mitigation steps (recommended, prioritized)
- Apply Microsoft’s security updates: check MSRC for the CB/KB and deploy patches via your normal patching channels — Windows Update, WSUS, SCCM/ConfigMgr, or your MDM. Microsoft’s advisory is the authoritative record for affected builds and KB numbers. (msrc.microsoft.com)
- Enable or verify Office’s Protected View for files from the internet and email attachments. Protected View prevents many parser paths from being executed with full privileges.
- Disable the Outlook/Explorer Preview Pane where practical until patches are applied, or block automatic previewers for risky filetypes (RTF, DOC, DOCX, DOTM). Several recent Office flaws have been exploitable via the Preview Pane.
- Harden client configurations:
- Disable macros by default.
- Enforce the principle of least privilege for users (don’t run day-to-day accounts with admin rights).
- Configure Attack Surface Reduction (ASR) rules and Exploit Protection policies in Windows Defender/endpoint products.
- Use mail-gateway and secure‑email features to strip or sandbox attachments from external senders (sandboxing unknown Office attachments will intercept many exploit attempts).
- Audit and restrict local file-sharing permissions in environments with shared workstations or multi‑user desktops (VDI). Local attackers or low‑privilege accounts are often the threat model for information‑disclosure bugs.
Detection and monitoring: what to look for
- EDR telemetry showing Word (winword.exe) crashes or unusual exceptions during document parsing.
- Unexpected child processes launched by winword.exe (cmd.exe, powershell.exe) — a common indicator of post‑exploit activity.
- Network egress from endpoints immediately following a Word process crash or abnormal memory-handling event.
- Alerts for accesses to in-memory secrets (credential caches, auth tokens) correlated with Word process events.
- Add rules to capture and retain stack traces from crashed Word processes and attach them to incident records.
- Monitor for instances of winword.exe invoking network sockets shortly after opening untrusted documents.
- Configure DLP/EDR to flag access to credential stores (e.g., LSASS dumps, token creation) when correlated with Office activity.
Enterprise patching playbook (practical steps)
- Inventory: enumerate all machines with Microsoft Word and identify update channels (Current Channel, Monthly Enterprise Channel, Semi-Annual Enterprise Channel, LTSC). Use SCCM/Intune reporting or your vulnerability management platform.
- Prioritize: focus first on externally facing systems, remote-work endpoints, VDI pools, and high-privilege accounts. Shared workstations used by multiple users should be prioritized because local attacks can be amplified.
- Test: validate the Microsoft patch in a staging / test group with your critical Office integrations (plugins, macros, document management systems).
- Rollout: stage deployment in phased waves and monitor for application compatibility. If the patch causes breaks, escalate to Microsoft support but maintain mitigations (disable preview, restrict attachment handling) until resolved.
- Verify: report and record KB/package versions and maintain evidence for audits (install dates, build numbers). Many organizations track patch deployment by mapping KB numbers to installed builds; Microsoft’s advisory page contains the official mapping. (msrc.microsoft.com)
Longer-term hardening and risk reduction
- Move to modern update models where possible: Contemporary Office update channels receive security fixes quickly; LTSC and older perpetual-license installs often lag and present larger risk. Regularly evaluate the trade-offs of moving to an evergreen update model.
- Embrace least‑privilege desktops and application control (AppLocker/WDAC) to limit what an exploited process can do. App control mitigations reduce the value of a local compromise.
- Use content disarm and reconstruction (CDR) or sandboxing on inbound Office documents for high-risk users (finance, HR, executive teams). Sandboxing deceptive attachments reduces the chance a crafted file will reach a production client in exploitable form.
- Educate users with phishing simulations that include malicious document vectors (not just links), because many Office bugs still rely on document delivery as the initial vector.
What we checked — and where more information is needed
- The Microsoft Security Update Guide entry the user provided lists CVE‑2025‑53736 with a short advisory summary identifying it as a Word information-disclosure flaw; that advisory is the authoritative source for affected builds and KB numbers. Administrators should consult the MSRC page for the official patch identifiers before deployment. (msrc.microsoft.com)
- Independent public indexing of CVE‑2025‑53736 (for example, NVD, CISA, or vendor‑neutral trackers) did not yield a detailed technical write‑up at the time of this article. That may be due to indexing lag, the advisory being newly published, or the vendor intentionally limiting technical detail until patches are widely installed. If technical PoCs or third‑party analyses appear, they should be reviewed immediately; in the interim vendor guidance is the authoritative directive. (nvd.nist.gov, cisa.gov)
Practical checks and commands for administrators
- Inventory Office versions:
- Use your management tool (SCCM, Intune, Jamf) to pull the Office Click-to-Run build or MSI version across endpoints. Confirm devices are on a supported update channel.
- Verify patch installation:
- On a client: open Word → File → Account → About Word to view the current build.
- For enterprise-wide checks: query your software inventory to match the KB/build IDs listed on MSRC (use PowerShell, SCCM compliance reports, or Intune device configuration reports). (msrc.microsoft.com)
- Temporarily disable the Preview Pane in Outlook/Explorer:
- Outlook: View → Reading Pane → Off (or configure via GPO/Intune policy).
- Explorer: View → Preview Pane → toggle off, or push policy that disables preview handlers for Office file types.
Why information disclosure matters even when it’s not RCE
An information‑disclosure vulnerability is not “less important” simply because it does not directly yield code execution. Leaked memory can:- Reveal credentials or session tokens that allow lateral movement.
- Provide memory addresses and pointers, dramatically simplifying exploitation of other memory‑corruption bugs.
- Expose sensitive business data that violates compliance and privacy obligations.
Recommendations for security teams (TL;DR checklist)
- Patch immediately via your standard tested rollout. (msrc.microsoft.com)
- Disable or restrict Preview Pane and enforce Protected View for untrusted documents.
- Harden endpoints (least privilege, ASR rules, app control).
- Sandbox or detonate inbound Office attachments for high-risk recipients.
- Tune EDR to detect suspicious winword.exe behavior and collect crash dumps/stack traces for analysis.
- Maintain audit evidence of patch deployment and mitigation timelines for compliance and incident response.
Conclusion
CVE‑2025‑53736 is a Word buffer over‑read information‑disclosure issue that fits a wider pattern of 2025 Office vulnerabilities: complex parsing code, preview/preview‑pane features, and document delivery continue to be exploitable vectors. Microsoft’s advisory is the authoritative source for affected builds and remediation; administrators should apply the vendor’s updates without delay, enable Protected View and preview restrictions as interim mitigations, and harden endpoints to reduce the value of any leaked memory. Where independent technical analyses are not yet publicly available, rely on vendor guidance and behavior‑based monitoring while keeping an eye out for third‑party write‑ups and EDR signatures that may appear as researchers analyze the patch. (msrc.microsoft.com, nvd.nist.gov)End of report.
Source: MSRC Security Update Guide - Microsoft Security Response Center