CVE-2026-42177

MEDIUMNVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 86% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
5.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.3Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
5.3
EG Score
5.3(medium)
EPSS
14.3%
KEV
Not listed

Published

May 12, 2026

Last Modified

May 13, 2026

Advisory Details (1)

Auto-updated Jun 16, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

Chrome declarativeNetRequest urlFilter is substring-matched in linux-entra-sso; PRT SSO cookie can leak to attacker-controlled hosts when broad host permissions are granted · Advisory · siemens/linux-entra-sso · GitHub

https://github.com/siemens/linux-entra-sso/security/advisories/GHSA-52rj-42vh-2rxc

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 10× in last 7d / 41× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 101 total refreshes for this CVE.

  1. 2026-07-16 17:03 UTCEPSS rescore
  2. 2026-07-16 00:53 UTCOSV refresh
  3. 2026-07-15 16:57 UTCEPSS rescore
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  24. 2026-06-28 01:29 UTCEG score recompute
  25. 2026-06-27 03:08 UTCEPSS rescore
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  1. 2026-06-26 20:44 UTCEG score recompute
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  3. 2026-06-25 13:49 UTCEPSS rescore
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  18. 2026-06-16 05:29 UTCEG score recompute
  19. 2026-06-15 17:49 UTCEPSS rescore
  20. 2026-06-15 00:00 UTCEG score recompute
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  22. 2026-06-13 23:00 UTCEPSS rescore
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  25. 2026-06-12 22:17 UTCEG score recompute
  26. 2026-06-11 22:57 UTCEG score recompute
  27. 2026-06-11 14:00 UTCEPSS rescore
  28. 2026-06-10 23:39 UTCEG score recompute
  29. 2026-06-10 22:18 UTCEPSS rescore
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  32. 2026-06-10 00:09 UTCEG score recompute
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  37. 2026-06-07 15:25 UTCEPSS rescore
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  39. 2026-06-07 02:14 UTCEG score recompute
  40. 2026-06-06 13:47 UTCEPSS rescore
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  42. 2026-06-06 02:56 UTCEG score recompute
  43. 2026-06-05 22:47 UTCEPSS rescore
  44. 2026-06-05 06:10 UTCEPSS rescore
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  46. 2026-06-05 03:38 UTCEG score recompute
  47. 2026-06-04 13:12 UTCEPSS rescore
  48. 2026-06-04 13:12 UTCEPSS rescore
  49. 2026-06-04 04:20 UTCEG score recompute
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  51. 2026-06-02 20:13 UTCEPSS rescore
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  53. 2026-06-01 13:52 UTCEPSS rescore
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  68. 2026-05-26 13:44 UTCEPSS rescore
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  71. 2026-05-23 00:07 UTCEG score recompute
  72. 2026-05-20 22:38 UTCEPSS rescore
  73. 2026-05-20 22:38 UTCEPSS rescore
  74. 2026-05-20 12:47 UTCEG score recompute
  75. 2026-05-20 11:22 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2026-42177?
CVE-2026-42177 is a medium vulnerability published on May 12, 2026. 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.SSOURL + "/*", i.e. "https://login.microsoftonline.com/*". Chrome's urlFilter without a |…
When was CVE-2026-42177 disclosed?
CVE-2026-42177 was first published in the National Vulnerability Database on May 12, 2026, with the most recent update on May 13, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-42177 actively exploited?
CVE-2026-42177 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 14.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-42177?
CVE-2026-42177 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-42177?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42177, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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