CVE-2026-7532: wolfSSL IP Address Name Constraints Bypass (CVSS 7.5)

Technical summary

CVE-2026-7532 is a certificate validation bypass affecting wolfSSL when compiled without the WOLFSSL_IP_ALT_NAME flag. The vulnerability exists in IP address name constraints enforcement—a X.509 feature that restricts certificates to specific IP ranges. When WOLFSSL_IP_ALT_NAME is not defined at compile time, wolfSSL does not properly validate these constraints, failing to reject certificates that violate the issuing CA's IP restrictions. This is classified as an improper certificate validation issue (CWE-295).

Business impact

Organizations relying on IP-restricted certificates for access control or identity validation may accept certificates from unauthorized sources. This is particularly impactful for infrastructure using certificate pinning, IP-based trust boundaries, or restricted certificate deployments in air-gapped or segmented networks. An attacker with access to a certificate bearing looser constraints than its intended use could impersonate legitimate services, bypass network access controls, or facilitate supply chain attacks in environments with certificate-based authentication.

Affected systems

wolfSSL instances compiled without the WOLFSSL_IP_ALT_NAME preprocessor flag are vulnerable. This includes embedded systems, IoT devices, and applications that perform custom builds of wolfSSL. Distributions using default or minimal configurations may be affected. Systems compiled with WOLFSSL_IP_ALT_NAME defined are not vulnerable to this bypass.

Exploitability

Exploitation requires possession of a valid certificate with weaker IP constraints than the target environment enforces, combined with network access to applications using the vulnerable wolfSSL configuration. The attack has a low attack complexity and requires no user interaction or privileges, making it straightforward for a motivated attacker with certificate access. However, the attacker must first obtain or create a certificate, and the flaw only manifests in unpatched, non-default builds.

Remediation

Update wolfSSL to a patched version (verify against the vendor advisory for the specific version addressing this flaw). Ensure the library is compiled with the WOLFSSL_IP_ALT_NAME flag enabled. Audit your build configurations to confirm IP address name constraint validation is active. Organizations using pre-built binaries should verify with their supplier that patches have been applied.

Patch guidance

Contact wolfSSL or check their security advisories for the corrected version. Recompile wolfSSL with WOLFSSL_IP_ALT_NAME defined if you maintain a custom build. Test the patched version in a non-production environment to confirm IP name constraint validation is enforced before rolling out. Document your build configuration to prevent regression to the vulnerable state.

Detection guidance

Review wolfSSL build logs and source configuration to identify if WOLFSSL_IP_ALT_NAME is defined. Examine running process and library versions. Implement certificate pinning or explicit IP validation at the application layer as a compensating control. Monitor for unexpected certificate acceptance in access logs. Test with a certificate that violates known IP constraints to verify enforcement is active.

Why prioritize this

This vulnerability scores HIGH (CVSS 7.5) due to its network-exploitable nature, low complexity, and significant integrity impact. It is not currently tracked in the CISA KEV catalog, but organizations with IP-restricted certificate deployments or certificate-based access controls should prioritize patching. The risk is highest in zero-trust, segmented, or air-gapped architectures where IP constraints are a critical security boundary.

Risk score, explained

CVSS 3.1 score of 7.5 reflects a remotely exploitable vulnerability (AV:N) with no special privileges or user interaction required (PR:N, UI:N). The attack scope is unchanged (S:U) but impact is high for integrity (I:H), as trust decisions may be compromised. Confidentiality and availability are not directly affected, limiting the score from critical. The vulnerability is not trivial to exploit in practice—it requires a valid certificate and specific deployment conditions—but the foundational nature of certificate validation elevates concern.

Frequently asked questions