# CVE-2026-42177: linux-entra-sso: linux-entra-sso is a browser plugin for Linux to SSO on Microsoft Entra ID

CVE-2026-42177 is fixed in linux-entra-sso on 1 platform by DEBIAN-CVE-2026-42177 (version 1.8.1-1), released May 27, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-42177
- Priority: Routine
- CVSS: 5.3 (medium)
- EPSS: 0.0023
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 12, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux-entra-sso Debian 14 | 1.8.1-1 | [DEBIAN-CVE-2026-42177](https://patchblox.com/security/data/fix/linux/debian-cve-2026-42177.md) | May 27, 2026 |

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Data as of 2026-11-09T07:25:28Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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