CVE-2026-42177CWE-284CWE-436

linux-entra-sso: PRT SSO cookie can leak to attacker-controlled hosts when broad host permissions are granted

Medium · published May 12, 2026

CVSS v3.1
5.3
EPSS
0%
Percentile
22.4
In the wild
Unconfirmed
What it is

linux-entra-sso is a browser plugin for Linux to SSO on Microsoft Entra ID. Prior to 1.8.1, platform/chrome/js/platform-chrome.js:69-88 registers a single declarativeNetRequest rule whose urlFilter is Platform.SSO_URL + "/*", i.e. "https://login.microsoftonline.com/*". Chrome's urlFilter without a | or || anchor is substring-matched against the full request URL. The same applied rule action is modifyHeaders that attaches the Entra ID Primary Refresh Token cookie. The Firefox adapter in platform/firefox/js/platform-firefox.js:53 performs a belt-and-braces startsWith(Platform.SSO_URL) check before injecting the header; the Chrome adapter does not. When the extension holds broad host permissions through the optional_host_permissions: ["https://*/*"] declared in platform/chrome/manifest.json:34, a main-frame navigation to a URL whose path embeds https://login.microsoftonline.com/ causes Chrome to attach the PRT cookie to the request to the attacker-controlled host. This vulnerability is fixed in 1.8.1.

The record
Technical detail
CVSS v3.1
5.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
CVSS v4.0
Not supplied
EPSS
0.00308 · 22.4th percentile
Weaknesses
CWE-284 · Improper Access Control; CWE-436 · Interpretation Conflict
Published
2026-05-12T17:11Z
EPSS history
Timeline
  • 12 MAY 17:11Z
    linux-entra-sso: PRT SSO cookie can leak to attacker-controlled hosts when broad host permissions are granted
    cvelistv5