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 85% 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
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.3Exploit: Elevated riskExposed: 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)
EG Risk
40(Track)
EG Risk 40/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity53% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
14%
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

Affected Packages

(1 across 1 ecosystem)
Debian:14(1)
PackageVulnerable rangeFixed inDependents
linux-entra-sso1.2.0-1 ... 1.8.1-1~bpo13+1 (7 versions)1.8.1-1—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 7× in last 7d / 26× 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 149 total refreshes for this CVE.

  1. 2026-09-13 16:47 UTCEPSS rescore
  2. 2026-09-12 15:01 UTCEPSS rescore
  3. 2026-09-11 14:53 UTCEPSS rescore
  4. 2026-09-11 10:23 UTCOSV refresh
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  18. 2026-08-23 18:11 UTCEG score recompute
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  25. 2026-08-17 10:49 UTCEG score recompute
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  1. 2026-08-16 14:56 UTCEPSS rescore
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  20. 2026-08-06 13:46 UTCEPSS rescore
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  22. 2026-08-05 19:17 UTCEPSS rescore
  23. 2026-08-04 15:10 UTCEPSS rescore
  24. 2026-08-04 10:38 UTCEPSS rescore
  25. 2026-08-02 22:19 UTCEG score recompute
  26. 2026-08-02 02:27 UTCEPSS rescore
  27. 2026-08-01 23:00 UTCEG score recompute
  28. 2026-08-01 04:16 UTCEPSS rescore
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  38. 2026-07-23 03:11 UTCEG score recompute
  39. 2026-07-22 14:08 UTCEPSS rescore
  40. 2026-07-21 15:24 UTCEPSS rescore
  41. 2026-07-20 17:08 UTCEPSS rescore
  42. 2026-07-19 14:31 UTCEPSS rescore
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  44. 2026-07-18 10:04 UTCEPSS rescore
  45. 2026-07-16 17:03 UTCEPSS rescore
  46. 2026-07-16 00:53 UTCOSV refresh
  47. 2026-07-15 16:57 UTCEPSS rescore
  48. 2026-07-15 02:00 UTCEPSS rescore
  49. 2026-07-13 22:30 UTCEPSS rescore
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  54. 2026-07-09 19:10 UTCEPSS rescore
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  67. 2026-06-28 04:56 UTCEPSS rescore
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  75. 2026-06-21 14:56 UTCEPSS rescore

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 0% probability of exploitation in the next 30 days, which ranks it in the top 85.6% of all scored CVEs.
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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