NCSC-2026-0289 [1.01] [H/H] Vulnerabilities patched in Microsoft Exchange Server

unknownpublic exploitCVE-2026-62911

Microsoft has patched vulnerabilities in Exchange Server. An attacker can exploit the vulnerabilities to perform a Denial-of-Service, impersonate other users, grant themselves elevated privileges, execute arbitrary code, and/or gain access to sensitive data. Update: For the vulnerability identified as CVE-2026-62911, proof-of-concept code has been published. This vulnerability allows an unauthenticated attacker to execute arbitrary code. As a result, the attacker can gain access to mailboxes of Exchange users, and the vulnerability can be exploited to perform further attacks on the victim's network.

CSIRTS triage

vendor: Microsoft product: Exchange Server Remote code execution Denial of service Authentication bypass Privilege escalation Information disclosure

What: Microsoft Exchange Server contains vulnerabilities allowing unauthenticated attackers to execute arbitrary code, deny service, impersonate users, escalate privileges, and access sensitive data; proof-of-concept code exists for CVE-2026-62911.
Who is affected: All Exchange Server deployments; CVE-2026-62911 affects unauthenticated remote attackers and can lead to mailbox access.
Urgency: Critical; proof-of-concept published for unauthenticated remote code execution vulnerability with immediate exploitation risk.
Action: Apply Microsoft security patches for CVE-2026-62911 and all related Exchange Server vulnerabilities immediately.

AI-assisted analysis generated from the source advisory — verify against the original.

⚡ Watch Exchange Server

Get an email when a new Exchange Server advisory drops — max one per day, one-click unsubscribe.

Details

Source: NCSC-NL Advisories (NL · national-cert · site)
Severity: unknown
Published: 2026-08-28
Exploitation: Not in CISA KEV at last sync
Language: Machine-translated to English — verify against the original

Original advisory: https://advisories.ncsc.nl/advisory?id=NCSC-2026-0289

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.

Low exploitation riskCVE-2026-629110.95% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 58% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-62911	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Microsoft Exchange Server

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

high[NEW] [high] Microsoft Exchange Server: Multiple vulnerabilitiescert-bund · 2026-09-01
criticalCVE-2026-65801: Server-side request forgery (ssrf) in Microsoft Exchange Online allows an unauthorized attacke…nvd · 2026-08-20
unknownNCSC-2026-0289 [1.00] [M/H] Vulnerabilities fixed in Microsoft Exchange Serverncsc-nl · 2026-08-12
mediumCVE-2026-65813: Server-side request forgery (ssrf) in Microsoft Exchange Server allows an authorized attacker …nvd · 2026-08-11
mediumCVE-2026-62915: Missing authorization in Microsoft Exchange Server allows an authorized attacker to bypass a s…nvd · 2026-08-11
highCVE-2026-62914: Improper neutralization of input during web page generation ('cross-site scripting') in Micros…nvd · 2026-08-11