CVE-2026-39324

CRITICAL EPSS 18.5%
Published Apr 7, 20262mo ago · Modified Jun 17, 20261w ago
9.3 CVSS 4.0
Critical
Find Similar
Published Apr 7, 2026 2mo ago
Last Modified Jun 17, 2026 1w ago

Description

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.

CVSS Details

Base Score
9.3
Exploitability
—
Impact
—
Vector string
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope X

Threat Intelligence

EPSS Exploit Probability
18.5% percentile
Exploit & Patch Status
No Known Exploit
No Patch Available

Weaknesses 4

CWE-287 Improper Authentication Authentication
CWE-345
CWE-502 Deserialization of Untrusted Data Validation
CWE-565

Affected Products 1

VendorProductVersionRange
rackrack-session*≥2.0.0  –  <2.1.2

References 1

  • github.com https://github.com/rack/rack-session/security/advisories/GHSA-33qg-7wpp-89cq
    MitigationVendor Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.