Man-in-the-Middle Vulnerability in wolfSSL Product
CVE-2026-5500

8.7HIGH

Key Information:

Vendor

Wolfssl

Status
Wolfssl
Vendor
CVE Published:
10 April 2026

What is CVE-2026-5500?

The vulnerability in wolfSSL's wc_PKCS7_DecodeAuthEnvelopedData() function arises from inadequate sanitization of the AES-GCM authentication tag length. This oversight allows a man-in-the-middle attacker to truncate the Message Authentication Code (MAC) field from its expected 16 bytes down to as low as 1 byte, which significantly weakens the integrity check. Consequently, this flaw reduces the security level of the MAC verification, making it easier for attackers to forge valid messages while evading detection.

Affected Version(s)

wolfSSL 0 <= 5.9.0

References

https://github.com/wolfSSL/wolfssl/pull/10102

CVSS V4

Score:
8.7
Severity:
HIGH
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Calif.io in collaboration with Claude and Anthropic Research
.