CVE-2026-7511: wolfSSL PKCS#7 Signature Forgery Vulnerability (CVSS 7.5)

Technical summary

CVE-2026-7511 is a cryptographic binding vulnerability in the PKCS#7_verify function affecting wolfSSL. The defect resides in how signer identity is associated with signature data during verification. An attacker can craft a malicious PKCS#7 structure where the signer field is not properly validated or bound to the signature content, allowing a forged signature to pass verification checks. The vulnerability is rooted in CWE-347 (Improper Verification of Cryptographic Signature), indicating a fundamental failure in signature validation logic rather than encryption strength.

Business impact

Any system relying on wolfSSL for signature verification in cryptographic workflows faces authentication bypass risk. This includes code signing, document authentication, certificate chain validation, and secure communications. An attacker could forge signatures to impersonate legitimate signers, potentially distributing malicious code, tampering with signed documents, or establishing fraudulent communications channels. Organizations using wolfSSL for mission-critical signature verification should treat this as a trust-breaking vulnerability.

Affected systems

wolfSSL versions using the vulnerable PKCS#7_verify function are affected. Verify the exact version ranges against the wolfSSL security advisory. Exposure is highest in embedded systems, IoT devices, and applications performing signature-based authentication or code integrity checks using wolfSSL.

Exploitability

The vulnerability scores CVSS 7.5 (HIGH) with zero-complexity attack and no authentication required. Network-accessible services processing PKCS#7 signatures are immediately at risk. No user interaction is needed. The relatively straightforward nature of signature verification means exploitation is likely practical for competent attackers, though active exploitation in the wild is not yet documented.

Remediation

Update wolfSSL to a patched version released after 2026-06-25. Verify the specific version number against wolfSSL's official security advisory. Organizations unable to patch immediately should: (1) restrict network access to signature verification services, (2) implement additional identity verification layers beyond signature alone, (3) monitor for abnormal signing activity, and (4) consider temporary disabling of PKCS#7 signature verification if feasible.

Patch guidance

Contact wolfSSL directly or visit their security advisory page for the specific patched version. Apply updates across all systems running vulnerable versions. Test signature verification workflows in staging before production rollout to ensure no unexpected behavior changes. Organizations with embedded or firmware-based wolfSSL integrations should prioritize patching, as updates may require longer deployment cycles.

Detection guidance

Monitor for anomalous PKCS#7 signature validation successes, particularly on documents or code with unexpected signers. Log all signature verification events and flag cases where signer identity diverges from expected patterns. Network-level detection is difficult; focus on behavioral indicators: unexpected code execution from newly-signed binaries, signed documents from unfamiliar entities, or successful verification of signatures that should have failed validation.

Why prioritize this

This is a HIGH-severity cryptographic trust failure with zero-complexity exploitation and no authentication barrier. The signer confusion directly undermines the authentication and non-repudiation properties that organizations depend on. Any environment where signature verification is security-critical should treat patching as urgent, particularly before the vulnerability appears on CISA's Known Exploited Vulnerabilities (KEV) list or is weaponized.

Risk score, explained

CVSS 7.5 reflects the vulnerability's network accessibility, low attack complexity, and high integrity impact. The absence of confidentiality impact (attacker cannot decrypt data) prevents a critical rating, but the ability to forge signatures and bypass authentication justifies HIGH severity. The lack of user interaction or privilege escalation requirements keeps the attack surface broad. Organizational context—reliance on signatures for authentication decisions—may justify treating this above its base score.

Frequently asked questions