CVE-2026-91187

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Source
https://cve.org/CVERecord?id=CVE-2026-91187
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-91187.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-91187
Aliases
Downstream
Published
2026-09-24T13:20:52Z
Modified
2026-09-25T03:48:51Z
Severity
  • 9.3 (Critical) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:N CVSS Calculator
Summary
Improper Verification of Cryptographic Signature in dashbit nimble_zta Cloudflare strategy
Details

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.

Database specific 
{
    "cna_assigner":  "EEF",
    "cwe_ids":  [
        "CWE-347"
    ],
    "osv_generated_from":  "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/91xxx/CVE-2026-91187.json",
    "unresolved_ranges":  [
        {
            "extracted_events":  [
                {
                    "introduced":  "bc004b70985ae5763901baab3a4e204047899768"
                },
                {
                    "fixed":  "6458fd18a5ba41166d4973214c519e98fe05b72d"
                }
            ],
            "source":  "AFFECTED_FIELD"
        }
    ]
}
References

Affected packages

Git / github.com/dashbitco/nimble_zta

Affected ranges

Type
GIT
Repo
https://github.com/dashbitco/nimble_zta
Events
Introduced
c1a084dd5ebe58bebfccb7bb8773f6dc280885bd
Fixed
d515550552873410849ea208fd193e27f00058ad
Database specific
Show details 
{
    "extracted_events":  [
        {
            "introduced":  "0.1.2"
        },
        {
            "fixed":  "0.1.3"
        }
    ],
    "source":  "AFFECTED_FIELD"
}

Affected versions

v0.*
v0.1.2

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-91187.json"