Halo through 2.26.1 Open Redirect via Unvalidated URI Parameter

Advisories

Halo through 2.26.1 Open Redirect via Unvalidated URI Parameter

severity: medium
date: 9/14/2026
Affecting: halo <= 2.26.1
CVE: CVE-2026-91772
CWE: CWE-601 URL Redirection to Untrusted Site ('Open Redirect')
CVSS: 5.3
CVSS V4 Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
References: https://github.com/halo-dev/halo/issues/10247
https://github.com/halo-dev/halo/blob/v2.26.1/application/src/main/java/run/halo/app/core/endpoint/theme/ThumbnailEndpoint.java#L76-L98
https://github.com/halo-dev/halo/blob/v2.26.1/application/src/main/resources/extensions/role-template-anonymous.yaml#L53-L55
https://github.com/halo-dev/halo
Credit: George Chen
Description: Halo through 2.26.1 contains an open redirect vulnerability in the anonymous thumbnail endpoint that fails to validate the uri query parameter. Attackers can craft malicious links on the trusted Halo domain that redirect visitors to arbitrary external sites, enabling phishing attacks and abuse of redirect-based trust relationships.

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