Microsoft Office
CVE-2009-0556
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.
What this means for your business
- It affects Microsoft Office. It matters if your company, or a supplier that handles your data, runs it.
- Attackers are already using it. CISA added it to its list of flaws used in real attacks on 7 January 2026.
- FIRST's prediction model gives it a 67% chance of attack attempts being seen in the next 30 days, ranking above 99% of all known flaws.
What to do
- 1Check whether your company or your suppliers run Microsoft Office.
- 2If you do, follow CISA's required action below. No patch reference has been published yet.
- 3Treat it as urgent. US federal agencies must fix it by 28 January 2026. That deadline does not apply to private companies, but it shows how seriously CISA takes it.
- 4Because attackers have used it, check the affected systems for signs of a break-in, not only for the update.
Fastnexa security experts
Attackers are already using this flaw. Is your Microsoft Office exposed?
Tell us where you run Microsoft Office and a Fastnexa penetration tester will check whether this flaw, or others like it, can be used against your websites, apps and network.
The full test is free for our first 10 founding clients until 31 December 2026. See the offer
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Required action
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA’s wording, unedited.
Scoring
- CVSS
- Not yet scored
Dates
- Published
- 2026-01-07
- Added to KEV
- 2026-01-07
- Remediation due
- 2026-01-28
- Sources
- CISA KEV