CVE-2026-5500
Published: 10 April 2026
Summary
CVE-2026-5500 is a medium-severity Improper Input Validation (CWE-20) vulnerability in Wolfssl Wolfssl. Its CVSS base score is 5.9 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Adversary-in-the-Middle (T1557); ranked at the 23.5th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
Threat & Defense at a Glance
Threat & Defense Details
Likely Mitigating ControlsAI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Security testing and developer training directly verify and enforce proper input validation, reducing exploitability of injection and malformed-data weaknesses.
Security testing and evaluation at multiple SDLC stages directly detects missing or flawed input validation, with the required remediation process ensuring fixes are applied.
Directly implements checks on information inputs to reject invalid data before processing.
Spam protection mechanisms perform filtering and detection on inbound/outbound messages, directly compensating for missing or weak input validation of unsolicited content.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Vulnerability explicitly enables MITM forgery of AES-GCM authenticated data by weakening tag validation.
NVD Description
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.
Deeper analysisAI
CVE-2026-5500 is a vulnerability in the wolfSSL cryptographic library, specifically within the wc_PKCS7_DecodeAuthEnvelopedData() function. The issue arises from improper sanitization of the AES-GCM authentication tag length received, with no lower bounds check implemented. This flaw, classified under CWE-20 (Improper Input Validation), allows the tag length to be manipulated, undermining the integrity of authenticated enveloped data processing.
A man-in-the-middle (MITM) attacker can exploit this vulnerability by truncating the MAC field from its standard 16 bytes to as little as 1 byte. This reduces the effective security of the authentication tag check from 2^{-128} to 2^{-8}, enabling feasible forgery of authenticated data. The CVSS v3.1 base score of 5.9 (AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N) indicates network accessibility with high attack complexity, no privileges or user interaction required, and high impact on integrity.
Mitigation is provided via a patch in the wolfSSL GitHub repository at https://github.com/wolfSSL/wolfssl/pull/10102, which corrects the lack of bounds checking and proper sanitization in the affected function.
Details
- CWE(s)