Microsoft DirectX NULL Byte Overwrite Vulnerability (CVE-2009-1537)

Severity Assessment

• Exploitability: 8/10 — NVD scores CVE-2009-1537 as CVSS 3.1 8.8 (HIGH), with network attack vector and no privileges required, but user interaction is required.

• Impact: 9/10 — Microsoft describes remote code execution with potential complete system compromise under administrative user context.

• Weaponization Risk: 8/10 — NVD records exploitation in the wild in May 2009, and CISA later added the CVE to KEV.

• Patch Urgency: 8/10 — Microsoft published an update in MS09-028 and CISA sets a KEV remediation due date of 2026-06-03 for applicable organizations.

• Detection Coverage: 4/10 — Public sources describe exploit conditions and mitigations but do not provide stable IOC sets for signature-only detection.

Summary

CVE-2009-1537 is a remote code execution vulnerability in Microsoft DirectShow’s QuickTime parsing path, described by Microsoft as a NULL byte overwrite issue. NVD states the flaw affects DirectX 7.0 through 9.0c on supported legacy Windows platforms and can be triggered with a specially crafted QuickTime media file.

Microsoft bulletin MS09-028 states that successful exploitation could grant the attacker the same rights as the current user, including full control when the user has administrative privileges. Microsoft also notes users with lower-privilege accounts may be less impacted.

CISA KEV lists this vulnerability as actively exploited, with known ransomware campaign use marked Unknown.

Exploit Chain

Stage 1: Delivery

The attacker provides a specially crafted QuickTime media file through email, web content, or another delivery path that causes the target system to process the file.

Stage 2: Parser Trigger

Microsoft and NVD describe a weakness in DirectShow QuickTime parsing behavior (including the QuickTime Movie Parser Filter in quartz.dll), enabling memory corruption conditions during media parsing.

Stage 3: Code Execution

When the crafted media content is opened, the vulnerability can lead to remote code execution in the user’s context. If the user has administrative rights, system compromise impact is higher.

Detection Guidance

1. Prioritize patch compliance for systems covered by MS09-028 and confirm the applicable DirectX update has been deployed.
2. Investigate workflows where untrusted QuickTime media files are opened or previewed.
3. Monitor for suspicious process behavior associated with media parsing workflows and follow-on code execution.
4. If immediate patching is not possible, apply Microsoft-documented workaround controls for QuickTime parsing in quartz.dll until updates are deployed.
5. Enforce least-privilege user accounts to reduce post-exploitation impact.

Indicators of Compromise

Public primary sources for CVE-2009-1537 do not provide a canonical IOC bundle (for example, stable hashes or network signatures) specific to this exploit path.

Useful operational indicators include:

• Evidence of users opening untrusted or unexpected QuickTime media content.
• Crash or anomalous behavior during DirectShow QuickTime parsing paths.
• Subsequent execution behavior consistent with user-context remote code execution on unpatched systems.

Disclosure Timeline

2009-05-29 — Public CVE publication

NVD records CVE-2009-1537 publication and describes in-the-wild exploitation conditions in May 2009.

2009-06-09 — Microsoft security bulletin and update

Microsoft releases MS09-028 addressing CVE-2009-1537 (plus CVE-2009-1538 and CVE-2009-1539), including workaround and mitigation guidance.

2026-05-20 — CISA KEV addition

CISA adds CVE-2009-1537 to the Known Exploited Vulnerabilities catalog with a remediation due date of 2026-06-03.

Sources & References

• Cybersecurity and Infrastructure Security Agency: Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency, 2026-05-20
• National Vulnerability Database: CVE-2009-1537 Detail — National Vulnerability Database, 2009-05-29
• Microsoft: Security Bulletin MS09-028 — Microsoft, 2009-06-09