CVE-2026-75757: AshAdmin cookie reader matches names by substring, enabling actor/session shadowing from a sibling subdomain

Severity: high (CVSS 8.3 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-31 · updated 2026-09-01
Weakness: CWE-565

Description

Reliance on Cookies without Validation and Integrity Checking vulnerability in ash-project ash_admin lets an attacker who controls a sibling subdomain rebind an admin's session to a different actor, tenant, or authorization mode. AshAdmin's client JavaScript read its state cookies (tenant, actor_resource, actor_primary_key, actor_action, actor_domain, actor_authorizing, actor_paused) by matching the cookie name with an unanchored regular expression (new RegExp(name + "=([^;]+)")) against the whole document.cookie. Any cookie whose name merely ends with the requested name therefore matches, and whichever is serialized first wins. Because cookies are shared across a registrable domain, a compromised sibling subdomain can set a shadowing cookie (for example xactor_authorizing) with Domain=.example.com that flows unvalidated into the admin's LiveSocket connect params. The fix matches cookie names by exact equality. This issue affects ash_admin: from 0.9.1 before 1.3.1.

Affected products

ash-project ash_admin: from 0.9.1 before 1.3.1 — fixed in 1.3.1

How to fix

Upgrade to a fixed version: ash-project ash_admin 1.3.1. Check the vendor advisory for mitigations.

References

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