dbcve.org
Improper Access ControlWeakness · CWE-284

CVE-2026-42177

MEDIUM · 5.3 CVSS v3.1 Published 2026-05-12
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
60/100
Remediation priority · Elevated
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The linux-entra-sso Chrome extension has a URL matching vulnerability where the declarativeNetRequest rule's urlFilter performs substring matching rather than anchored matching. Combined with broad host permissions (https://*/*), any main-frame navigation to a URL whose path contains 'https://login.microsoftonline.com/' causes Chrome to attach the Entra ID Primary Refresh Token cookie to requests destined for attacker-controlled hosts.

MitigationUpdate to version 1.8.1 which includes proper URL anchoring in the declarativeNetRequest rule, or ensure the extension's host permissions are scoped appropriately to prevent credential leakage.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed extension version
    Open Chrome and navigate to chrome://extensions, enable Developer mode, locate the linux-entra-sso extension, and record the version number displayed
    Affected if the version number is lower than 1.8.1
  2. Inspect extension host permissions
    In the same extensions page, click on the linux-entra-sso extension details and review the Permissions section, specifically the Host permissions field
    Affected if the host permissions include a broad pattern such as 'https://*/*' or 'https://*/*' without specific domain restrictions
  3. Locate declarativeNetRequest rule configuration
    Extract the extension's manifest.json file from the extension package (available in the extensions folder) and locate the declarative_net_request rule configuration section
    Affected if the urlFilter field contains a pattern that performs substring matching (e.g., checks for 'login.microsoftonline.com' anywhere in the URL) without proper anchors like ^ or domain anchors
  4. Verify URL matching behavior
    Examine the urlFilter value in the rules - check if it uses unanchored substring matching like 'login.microsoftonline.com' rather than anchored patterns such as '^https://login\.microsoftonline\.com/'
    Affected if the urlFilter uses plain substring matching without start (^) and end ($) anchors, allowing the pattern to match URLs where 'login.microsoftonline.com' appears anywhere in the path

A user is affected if the extension version is below 1.8.1 AND the extension has broad host permissions (https://*/*) AND the declarativeNetRequest rule's urlFilter performs unanchored substring matching on 'login.microsoftonline.com'.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update to version 1.8.1 which includes proper URL anchoring in the declarativeNetRequest rule, or ensure the extension's host permissions are scoped appropriately to prevent credential leakage.

Recommended fix High confidence

1.8.1

  1. 1. Identify the currently installed version of linux-entra-sso browser extension
  2. 2. Upgrade the linux-entra-sso extension to version 1.8.1 or later
  3. 3. Verify the upgrade was successful by checking the extension version in Chrome's extensions management

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-42177 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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