Affects widely deployed Microsoft SharePoint with high severity (CVSS 9.3); XSS can enable enterprise-wide session/credential theft and impersonation.
CVE-2026-70306
XSS in Microsoft SharePoint enabling UI spoofing and session hijack
Is CVE-2026-70306 being exploited?
Not confirmed. CVE-2026-70306 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 0.75% probability of exploitation in the next 30 days.
How severe is CVE-2026-70306?
CVE-2026-70306 is rated Critical with a CVSS score of 9.3. 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-2026-70306?
Yes. A fix has been recorded for CVE-2026-70306. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-70306 affect?
CVE-2026-70306 affects Microsoft Office SharePoint, SharePoint Server, SharePoint Online. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-70306?
Apply vendor patch immediately; if unavailable, deploy WAF rules, CSP, and strict input validation.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote cross-site scripting lets attackers run JS in users' browsers to spoof UI, steal sessions/credentials, or perform actions as the user.
Immediate action required
- affected>= 16.0.0 and < 16.0.5565.1001
- affected>= 16.0.0 and < 16.0.10417.20198
- affected>= 16.0.0 and < 16.0.19725.20522
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.