Skip to content
OpenAdvisories
Medium · 5.3 CVE-2026-42177 EUVD-2026-29703

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

Published May 12, 2026 · Updated May 13, 2026 · Assigned by GitHub_M

Description

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.

Affected products

VendorProductAffectedFixed
siemens linux-entra-sso < 1.8.1 —

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Debian 14 linux-entra-sso 1.8.1-1 —
ReleasePackageFixed inAdvisory
Ubuntu 26.10 linux-entra-sso No fix yet —
Ubuntu 26.04 LTS linux-entra-sso No fix yet —

References