Threats / Microsoft / CVE-2009-0557
CVE-2009-0557
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
Microsoft Office vulnerability
Microsoft Office contains an object record corruption vulnerability in Excel that allows remote attackers to execute arbitrary code through crafted files.
Verdict
Today item — known-exploited.
A remote code execution vulnerability in Microsoft Office Excel triggered by malformed record objects in specially crafted spreadsheets. The vulnerability has been exploited in the wild and carries a high EPSS score of 0.86365, indicating significant practical exploitation risk.
CISA KEV Yes · 2022-06-084EPSS 0.58551 (verify live)5CVSS 7.8 (CISA)3CISA SSVC Exploitation: active · Automatable: no · Impact: total3
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
1 independent public report of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-06-08).
Probability (EPSS)
EPSS 0.58551 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 7.8 (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H) · Affected: Microsoft, Office. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-94 Code Injection — weakness family: Injection.CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 4746 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious Excel file with a corrupted object record and send it to a target user.
Business
An employee receives and opens the file, triggering remote code execution on corporate systems.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I exploit the code execution to establish persistence and move laterally within the network.
Business
Attackers gain unauthorized access to sensitive data, intellectual property, and critical business systems.
3
Lateral reach — past segmentation narrative 3
Attacker
I exfiltrate confidential information or deploy additional malware across the compromised infrastructure.
Business
The organization faces data breaches, operational disruption, regulatory penalties, and reputational damage.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05