Improper Verification of Cryptographic Signature in dashbit nimble_zta Cloudflare strategy (CVE-2026-91187) | HOL Guard CVE

Critical · CVSS 9.3CVE-2026-91187

Improper Verification of Cryptographic Signature in dashbit nimble_zta Cloudflare strategy

Answer in brief

CVE-2026-91187 records a Critical severity (CVSS 9.3) vulnerability in Improper Verification of Cryptographic Signature in dashbit nimble_zta Cloudflare strategy. The current sources do not mark it as known exploited. The current feed maps dashbit/dashbitco/nimble_zta (generic), dashbit/nimble_zta (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 24, 2026Updated Sep 24, 2026Source checked Sep 24, 2026First seen by HOL Sep 24, 2026Material review Sep 24, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.3
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 9.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps dashbit/dashbitco/nimble_zta (generic), dashbit/nimble_zta (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
dashbit/dashbitco/nimble_ztageneric	>=bc004b70985ae5763901baab3a4e204047899768 <6458fd18a5ba41166d4973214c519e98fe05b72d	6458fd18a5ba41166d4973214c519e98fe05b72d
dashbit/nimble_ztageneric	>=0.1.2 <0.1.3	0.1.3

Recommended response

Check inventory. Check lockfiles and deployed manifests for dashbit/dashbitco/nimble_zta, dashbit/nimble_zta.
Review the reported fix. Source-reported workaround: Disable the Cloudflare authentication strategy. To keep the user identity strategy available, reject the service token requests yourself. Examine each request before you call NimbleZTA.Cloudflare.authenticate/3, and reject it if its JWT carries the common_name claim and the type claim.

Evidence timeline and material changes

Published upstream
Sep 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 24, 2026

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.