Microsoft Office PowerPoint Code Injection Vulnerability
CVE-2009-0556 is a security vulnerability in Microsoft Office, added to CISA KEV on January 7, 2026. Patch order: third of four.
What it is
Microsoft Office PowerPoint contains a code injection vulnerability that allows remote attackers to execute arbitrary code via a PowerPoint file with an OutlineTextRefAtom containing an invalid index value that triggers memory corruption.
VulnCheck tracked exploitation 6123 days before CISA's KEV listing. VulnCheck's broader catalog of in-the-wild exploitation evidence picked this up before it landed on CISA's formal list. Per-CVE fact about this entry; not a population claim about lead time in general.
Who's affected
Affects anyone using Microsoft 365 or Office to compose, store, or send email, documents, or spreadsheets. In a small practice, that's typically where client communications, engagement letters, and case notes live — credential compromise here means an attacker reads everything that platform stores.
What to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
The action above is CISA's wording. The directive it names, BOD 22-01, was revoked by BOD 26-04 on June 10, 2026; CISA's catalog still carries the older text for this entry.
If you don't have someone in-house to verify the patch deployed across every endpoint — or you're not sure whether you're affected — that's exactly the kind of triage we do. Book a free 20-minute triage call.
Insurance readiness
Your insurer will ask if this is patched.
Unpatched entries on CISA's Known Exploited Vulnerabilities list are exactly what cyber-insurance carrier questionnaires probe for, and knowing which controls they check is how you keep a renewal from stalling.
Get the free carrier questionnaire →Severity
CVSS base score: 8.8 — HIGH
Weakness classification: CWE-94
CISA due date
CISA's listed due date: January 28, 2026.
Federal civilian agencies work under CISA's Binding Operational Directive 26-04, which replaced BOD 22-01 on June 10, 2026. It sets the deadline for each affected system by:
- How exposed that system is to the internet
- Whether the attack can be automated
- How much control it gives an attacker
Its table gives catalogued vulnerabilities 3 or 14 days.
None of this binds a private business, but treat the date as a strong recommendation, especially if you handle regulated data (HIPAA, GLBA, ABA model rules).
EPSS
EPSS score: 67.3% — higher than 99% of all scored CVEs.
EPSS estimates the probability of exploitation activity in the next 30 days. Every entry on this site is already confirmed exploited, so read it as relative urgency among the things you still have open, not as permission to wait.
Other exploited Microsoft Office entries
More CISA KEV entries for Microsoft Office. Same product line, same actively-exploited status.
Source
This entry comes from CISA's Known Exploited Vulnerabilities catalog, public US-Government data we pull daily. The plain-language framing and the what-to-do guidance above are ours. View the original entry on cisa.gov.
