Vulnerability in linux-entra-sso (UBUNTU-CVE-2026-42177)

Summary

Vulnerability in linux-entra-sso (UBUNTU-CVE-2026-42177). Confidential information can be exposed externally. Mitigation: upgrade to 1.8.1 or later.

Original description

The description as published by the source.

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.

Source: OSV.dev (Open Source Vulnerabilities) OSV

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as UBUNTU-CVE-2026-42177 has been found in linux-entra-sso.
Confidential information can be exposed externally.
What to do: upgrade linux-entra-sso to 1.8.1 or later.
If unsure, ask your IT team or search "linux-entra-sso UBUNTU-CVE-2026-42177" on the vendor's site.

UBUNTU-CVE-2026-42177 (linux-entra-sso)
Attack vector: remote (network-reachable) / unauthenticated
Patched: 1.8.1 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (unclassified) exists in linux-entra-sso.

📍 Affected scope

Check the vendor advisory for the affected versions of linux-entra-sso.

🔥 Severity

Severity: ?. Confidential information can be exposed externally.

🔧 How to fix

Update to 1.8.1.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'linux-entra-sso' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

1
Identify exposure identify
```
grep -r 'linux-entra-sso' . | grep -v node_modules
```
リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で linux-entra-sso を grep し、稼働しているサービス・バージョンを把握する。
2
Apply patch patch
```
Upgrade linux-entra-sso to 1.8.1
```
ステージング環境で 1.8.1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
3
Post-deployment verification verify
```
Confirm patched version is live in production
```
パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

Ubuntu:26.04:LTS linux-entra-sso

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:26.10 linux-entra-sso

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

References

report ubuntu.com
report cve.org
report github.com