CVE-2026-91187
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.
Is your site exposed to CVE-2026-91187?
Run a free security scan — no signup, results in seconds.
EPSS — Exploit Prediction
EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.
Weakness Type (CWE)
References
Other References
Frequently Asked Questions
What is CVE-2026-91187? +
How do I check if I'm vulnerable to CVE-2026-91187? +
Related Vulnerabilities
DataEase is an open source data visualization and analysis tool. Prior to 2.10.23, DataEase enterprise token handling can let TokenFilter#doFilter() …
MikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures during X.509 validation. Because its trust store includes an e=3 root CA, an …
In Bouncy Castle for Java before 1.85, CMS verifySignatures returns true for SignedData with zero signers. This issue also affects …
In Bouncy Castle for Java before 1.85, RSA PKCS#1 verification skips last two hash bytes in NULL-omitted path. This issue …
OpenLearnX is an open-source, decentralized learning and assessment platform. Prior to 2.0.4, a critical authentication vulnerability was identified in OpenLearnX …
Hyperbridge is a hyper-scalable coprocessor for verifiable, cross-chain interoperability. A critical vulnerability was discovered in the ismp-grandpa crate, that allowed …
