Umbraco CMS before 17.7.2 and 18.2.2 Account Takeover via Host Header Poisoning
Summary
| CVE | CVE-2026-117553 |
|---|---|
| State | PUBLISHED |
| Assigner | VulnCheck |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-27 14:16:35 UTC |
| Updated | 2026-10-27 16:03:45 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 7.7 HIGH from [email protected]
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
Problem Types: CWE-601 | CWE-601 URL Redirection to Untrusted Site ('Open Redirect')
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 7.7 | HIGH | 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/C... |
| 4.0 | CNA | CVSS | 7.7 | HIGH | 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 |
| 3.1 | [email protected] | Primary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H |
| 3.1 | CNA | CVSS | 7.5 | HIGH | CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H |
CVSS v4.0 Breakdown
Attack Vector
NetworkAttack Complexity
LowAttack Requirements
PresentPrivileges Required
NoneUser Interaction
PassiveConfidentiality
HighIntegrity
HighAvailability
HighSub Conf.
NoneSub Integrity
NoneSub Availability
NoneCVSS: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
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
HighPrivileges Required
NoneUser Interaction
RequiredScope
UnchangedConfidentiality
HighIntegrity
HighAvailability
HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Umbraco | Umbraco-CMS | affected 17.7.2 semver | Not specified |
| CNA | Umbraco | Umbraco-CMS | affected 18.0.0 18.2.2 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| www.vulncheck.com/advisories/umbraco-cms-before-17.7.2-and-18.2.2-account-takeo... | [email protected] | www.vulncheck.com | |
| github.com/umbraco/Umbraco-CMS/commit/490b9b27dcbb8fb3fe868a36203590968b... | [email protected] | github.com | |
| github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-rpv9-qp4c-g469 | [email protected] | github.com | |
| github.com/umbraco/Umbraco-CMS | [email protected] | github.com | |
| github.com/umbraco/Umbraco-CMS/blob/release-18.2.1/src/Umbraco.Cms.Api.M... | [email protected] | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Eu Joe Chegne (Project Umbra) (en)
CNA: Damien Wong (Project Umbra) (en)
CNA: AndyButland (en)
There are currently no legacy QID mappings associated with this CVE.