CVE-2026-91187

CRITICALPre-NVD 9.39.3
EchelonGraph scoreLOW confidence

This critical-severity CVE scores 9.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). 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: secondary
9.3EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: —CVSS: 9.3Exploit: None knownExposed: 0

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

Improper Verification of Cryptographic Signature vulnerability in dashbit nimble_zta allows an unauthenticated remote attacker to authenticate as an arbitrary Cloudflare service token. Applications using the Cloudflare Zero Trust authentication strategy are affected.

verify_token/2 in lib/nimble_zta/cloudflare.ex matches the result of JOSE.JWT.verify/2 against {_, token, _s}, which discards the boolean verification result and returns the decoded token after a failed signature check. The attacker sends a forged JWT in the cf-access-jwt-assertion header, carrying the expected iss claim and the seven service token claims. verify_iss/2 reads the iss claim from the forged token, so it rejects nothing, and the service token path then returns those claims as the authenticated identity.

This issue affects nimble_zta: from 0.1.2 before 0.1.3.

CVSS v3
9.3
EG Score
9.3(low)
EG Risk
57(Track)
EG Risk 57/100SSVC: 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
Severity93% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
—
EPSS %ILE
—
KEV
Not listed

Published

September 24, 2026

Last Modified

September 24, 2026

Advisory Details (5)

Auto-updated Sep 24, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_commit.
github_commit

commit 6458fd18a5ba (dashbitco/nimble_zta)

Fix landed in dashbitco/nimble_zta commit 6458fd18a5ba — awaiting tagged release

https://github.com/dashbitco/nimble_zta/commit/6458fd18a5ba41166d4973214c519e98fe05b72d
github_commit

commit bc004b70985a (dashbitco/nimble_zta)

Fix landed in dashbitco/nimble_zta commit bc004b70985a — awaiting tagged release

https://github.com/dashbitco/nimble_zta/commit/bc004b70985ae5763901baab3a4e204047899768
generic🟡 PoC Available

OSV - Open Source Vulnerabilities

https://osv.dev/vulnerability/EEF-CVE-2026-91187
generic🟡 PoC Available

CVE-2026-91187

https://cna.erlef.org/cves/CVE-2026-91187.html
github Patch Available

Token bypass on CloudFlare Zero Trust Authentication · Advisory · dashbitco/nimble_zta · GitHub

Affected: version 0.1.3.

https://github.com/dashbitco/nimble_zta/security/advisories/GHSA-rj24-g8cc-g7g2

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 5× in last 7d / 5× 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.

  1. 2026-09-24 15:29 UTCEG score recompute
  2. 2026-09-24 14:57 UTCEG score recompute
  3. 2026-09-24 14:33 UTCEG score recompute
  4. 2026-09-24 13:29 UTCEG score recompute
  5. 2026-09-24 13:28 UTCMITRE cvelistV5first tracked

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Frequently asked(4)

What is CVE-2026-91187?
CVE-2026-91187 is a critical vulnerability published on September 24, 2026. Improper Verification of Cryptographic Signature vulnerability in dashbit nimble_zta allows an unauthenticated remote attacker to authenticate as an arbitrary Cloudflare service token. Applications using the Cloudflare Zero Trust authentication strategy are affected. verifytoken/2 in…
When was CVE-2026-91187 disclosed?
CVE-2026-91187 was first published in the National Vulnerability Database on September 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-91187?
CVE-2026-91187 has a CVSS v3 base score of 9.3 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-91187?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-91187, 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.

Dependency Blast Radius

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