CVE-2026-5500
Improper Validation of AES-GCM Authentication Tag Length in PKCS#7 Envelope Allows Authentication Bypass
Severity Score
8.7
*CVSS v4
Exploit Likelihood
*EPSS
Affected Versions
*CPE
Public Exploits
0
*Multiple Sources
Exploited in Wild
-
*KEV
Decision
Attend
*SSVC
Descriptions
wolfSSL's wc_PKCS7_DecodeAuthEnvelopedData() does not properly sanitize the AES-GCM authentication tag length received and has no lower bounds check. A man-in-the-middle can therefore truncate the mac field from 16 bytes to 1 byte, reducing the tag check from 2⁻¹²⁸ to 2⁻⁸.
*Credits:
Calif.io in collaboration with Claude and Anthropic Research
CVSS Scores
Attack Vector
Attack Complexity
Attack Requirements
Privileges Required
User Interaction
System
Vulnerable | Subsequent
Confidentiality
Integrity
Availability
* Common Vulnerability Scoring System
SSVC
- Decision:Attend
Exploitation
Automatable
Tech. Impact
* Organization's Worst-case Scenario
Timeline
- 2026-04-03 CVE Reserved
- 2026-04-10 CVE Published
- 2026-04-13 CVE Updated
- 2026-05-12 EPSS Updated
- ---------- Exploited in Wild
- ---------- KEV Due Date
- ---------- First Exploit
CWE
- CWE-20: Improper Input Validation