CVE-2026-55009: Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.
Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.
Details
Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-55009
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Moderate exploitation riskCVE-2026-550091.6% 30-day exploitation probability. Patch within normal cadence, watch for KEV listing. Riskier than 74% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-55009 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
- high[NEW] [high] Microsoft Exchange: Multiple vulnerabilitiescert-bund
- unknownMultiple vulnerabilities in Microsoft products (July 15, 2026)cert-fr-avis
- unknownNCSC-2026-0234 [1.00] [M/H] Vulnerabilities fixed in Microsoft Exchangencsc-nl
- highCVE-2026-55009: Microsoft Exchange Server Elevation of Privilege Vulnerabilitymsrc
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