CVE-2026-5500
Published: 10 April 2026
Summary
CVE-2026-5500 is a high-severity Improper Input Validation (CWE-20) vulnerability in Wolfssl Wolfssl. Its CVSS base score is 8.7 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Adversary-in-the-Middle (T1557); ranked at the 27.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SC-13 (Cryptographic Protection).
Deeper analysis
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.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-21293
Vulnerability details
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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Vulnerability explicitly enables MITM forgery of AES-GCM authenticated data by weakening tag validation.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires validation of inputs such as the AES-GCM authentication tag length before processing in wc_PKCS7_DecodeAuthEnvelopedData().
Mandates cryptographic integrity mechanisms that would be undermined by allowing a truncated 1-byte GCM tag to be accepted.
Requires correct implementation of approved cryptographic algorithms so that GCM tag verification retains its intended 128-bit strength.
Hardening callouts derived
Configuration rules from DISA STIG baselines that reduce the attack surface for weaknesses of the type cited by this CVE. Derived transitively via CVE→CWE→STIG over `controls_xwalks` (authoritative rows only).
Oracle Linux 8 (2 rules)
- V-248574 YUM must be configured to prevent the installation of patches, service packs, device drivers, or OL 8 system components that have not been digitally signed using a certificate that is recognized and approved by the organization. via CWE-20
- V-248575 OL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. via CWE-20
RHEL 7 (2 rules)
- V-204447 The Red Hat Enterprise Linux operating system must prevent the installation of software, patches, service packs, device drivers, or operating system components from a repository without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. via CWE-20
- V-204448 The Red Hat Enterprise Linux operating system must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. via CWE-20
RHEL 8 (2 rules)
- V-230264 RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components from a repository without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. via CWE-20
- V-230265 RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. via CWE-20