CVE-2026-39324

Rack::Session is a session management implementation for Rack. From 2.0.0 to before 2.1.2, Rack::Session::Cookie incorrectly handles decryption failures when configured with secrets:. If cookie decryption fails, the implementation falls back to a default decoder instead of rejecting the cookie. This allows an unauthenticated attacker to supply a crafted session cookie that is accepted as valid session data without knowledge of any configured secret. Because this mechanism is used to load session state, an attacker can manipulate session contents and potentially gain unauthorized access. This vulnerability is fixed in 2.1.2.

Database specific

{
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
        "CWE-287",
        "CWE-345",
        "CWE-502",
        "CWE-565"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39324.json"
}

References

Affected packages

Git / github.com/rack/rack-session

Affected ranges

Type

GIT

Repo

https://github.com/rack/rack-session

Events

Introduced

711c671ae6ed7b062bd875125314f676e2ad0116

Fixed

504367b59caf7ec78127785cc6351f46be14f8ca

Database specific

{
    "source": [
        "AFFECTED_FIELD",
        "CPE_RANGE"
    ],
    "extracted_events": [
        {
            "introduced": "2.0.0"
        },
        {
            "fixed": "2.1.2"
        }
    ],
    "cpe": "cpe:2.3:a:rack:rack-session:*:*:*:*:*:ruby:*:*"
}

Affected versions

v2.*

v2.0.0

v2.1.0

v2.1.1

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-39324.json"