Affects Microsoft Exchange, a widely deployed enterprise mail server; exploitable XSS can enable account/session theft and org-wide phishing, likely to impact many organizations.
CVE-2026-55008
XSS in Microsoft Exchange enabling web spoofing and session theft
Is CVE-2026-55008 being exploited?
Not confirmed. CVE-2026-55008 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.86% probability of exploitation in the next 30 days.
How severe is CVE-2026-55008?
CVE-2026-55008 is rated Critical with a CVSS score of 9.6. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-55008?
Yes. A fix has been recorded for CVE-2026-55008. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-55008 affect?
CVE-2026-55008 affects Microsoft Exchange Server (OWA/ECP/EWS). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-55008?
Apply Microsoft patch immediately; if unavailable, enable WAF/input filtering and block suspicious requests.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote XSS allowing attackers to spoof UI, steal session cookies, perform phishing and act as authenticated users in webmail.
Immediate action required
- affected>= 15.01.0.0 and < 15.01.2507.071
- affected>= 15.02.0.0 and < 15.02.1544.043
- affected>= 15.02.0.0 and < 15.02.1748.048
- affected>= 15.02.0.0 and < 15.02.2562.045
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.