CVE-2026-117553

Umbraco CMS before 17.7.2 and 18.2.2 Account Takeover via Host Header Poisoning

Published Oct 27, 2026 CVSS 4.0 · 7.7 High EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description 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.
Title Umbraco CMS before 17.7.2 and 18.2.2 Account Takeover via Host Header Poisoning
First Time appeared Umbraco
Umbraco umbraco Cms
Weaknesses CWE-601
CPEs cpe:2.3:a:umbraco:umbraco_cms:*:*:*:*:*:*:*:*
Vendors & Products Umbraco
Umbraco umbraco Cms
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H'}

cvssV4_0

{'score': 7.7, 'vector': '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
VulnCheck
Published
Updated
Nov 4, 2026, 3:56 PM
Reserved
Oct 27, 2026, 11:25 AM
Status
Awaiting Analysis
Published
Oct 27, 2026, 2:16 PM
Modified
Nov 4, 2026, 4:17 PM