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CVE-2026-117553

7.7 high Published
NVD · CVE.org

Umbraco CMS before 17.7.2 and 18.2.2 contains an authentication bypass vulnerability that allows unauthenticated attackers to register attacker-controlled OAuth redirect URIs by poisoning the Host header. Attackers send signed-in users authorization links using response_mode=form_post to capture codes, then redeem them via HTTP Basic client credentials to hijack back-office sessions and execute code through Razor templates.

Fix

Nothing published yet: no patch, vendor advisory or mitigation reference on NVD, no vendor advisory in the News for this CVE, not in CISA's KEV, no fixed package version. BaselineWatch does not guess at one.

Change history 6

  1. StatusAwaiting Analysis → PublishedNVD modified 2026-10-27 13:07
  2. StatusPublished → Awaiting AnalysisNVD modified 2026-10-27 16:03
  3. StatusReceived → PublishedNVD modified 2026-10-27 13:07
  4. StatusPublished → ReceivedNVD modified 2026-10-27 14:16
  5. CVSS7.7 (v4.0, CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N) → 7.7 (v4.0, CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X)NVD modified 2026-10-27 14:16
  6. First seenCVSS 7.7 · umbracoNVD modified 2026-10-27 13:07

Affected (CPE criteria) 0

NVD has not attached CPE configurations yet.

References 5