wolfSSL’s team has disclosed a sweeping set of vulnerabilities in the widely deployed wolfSSL embedded SSL/TLS library, with several flaws enabling complete certificate chain bypass, allowing attackers to present fraudulent certificates that are accepted as valid by affected applications.
The most severe vulnerabilities, CVE-2026-11310 and CVE-2026-11999, both rated High, target the OpenSSL compatibility certificate verifier (wolfSSL_X509_verify_cert()) in builds compiled with --enable-opensslextra.
Multiple wolfSSL Vulnerabilities
CVE-2026-11310 affects versions v5.8.4, v5.9.0, and v5.9.1, introduced via commit 025dbc34, where untrusted intermediate certificates were temporarily loaded into the certificate manager but not dropped before the trusted-store check.
CVE-2026-11999, affecting v5.7.4 through v5.9.1, exploits path-depth exhaustion: the verifier returns success when the chain depth exceeds 100 links, even if no trusted anchor is ever reached.
A third critical bypass, CVE-2026-5501 (High), also in the OpenSSL compatibility layer, allows attackers to forge a certificate for any subject name with any public key using merely a valid leaf certificate from a trusted CA such as Let’s Encrypt; the leaf’s signature is never checked when an untrusted intermediate carrying CA:FALSE is supplied.
CVE-2026-55960 (High) allows an un-negotiated Raw Public Key (RFC 7250) to be accepted in place of an X.509 certificate, bypassing chain validation entirely. This affects builds with HAVE_RPK enabled, which is included in --enable-all builds.
Separately, CVE-2026-6091 (Medium) allows partial-chain certificate verification to terminate at an attacker-controlled untrusted intermediate rather than a trusted root anchor, and CVE-2026-55964 (Medium) permits a chain-supplied intermediate asserting CA:TRUE but lacking keyCertSign to be accepted as a valid signing CA.
High-Severity Memory Corruption Flaws
Beyond chain bypass issues, the disclosure includes several memory corruption vulnerabilities affecting broader deployment scenarios:
- CVE-2026-6679 (High): Heap buffer overflow in DTLS 1.3 ACK serialization due to integer truncation, triggerable before peer authentication affects wolfSSL 5.9.0 and earlier
- CVE-2026-55958 (High): Out-of-bounds write in the Renesas TSIP TLS 1.3 transcript buffer via a missing
returnafter bounds check failure, corrupting adjacent heap state - CVE-2026-5194 (Critical): Missing hash/digest size and OID checks allow undersized digests to be accepted in signature verification across ECDSA, DSA, ML-DSA, ED25519, and ED448, reported by Nicholas Carlini from Anthropic
Several medium-severity flaws further erode certificate trust enforcement. CVE-2026-6731 allows X.509 name constraint bypass via the Subject Common Name when treated as a DNS-type name.
CVE-2026-10592 confirms that wildcard DNS SANs (e.g., *.example.com) bypassed CA name-constraint checks entirely in affected builds.
Additionally, CVE-2026-6291 describes a Bleichenbacher padding oracle in PKCS#7 KTRI decryption, where distinguishable error codes could allow an attacker to incrementally recover the Content Encryption Key (CEK).
Affected Versions and Remediation
| CVE | Severity | Affected Versions | Fixed In |
|---|---|---|---|
| CVE-2026-11310 | High | v5.8.4, v5.9.0, v5.9.1 | 5.9.2 |
| CVE-2026-11999 | High | v5.7.4 – v5.9.1 | 5.9.2 |
| CVE-2026-55960 | High | --enable-all builds | 5.9.2 |
| CVE-2026-5501 | High | OpenSSL compat layer | 5.9.1 |
| CVE-2026-5194 | Critical | Pre-5.9.1 | 5.9.1 |
| CVE-2026-6679 | High | v5.9.0 and earlier | 5.9.1 |
| CVE-2026-6091 | Medium | Pre-5.9.2 | 5.9.2 |
wolfSSL has released version 5.9.2, which patches all disclosed vulnerabilities. Organizations using wolfSSL in TLS clients, servers, embedded IoT systems, or OpenSSL compatibility API contexts are strongly advised to upgrade immediately.
Developers should audit build flags particularly --enable-opensslextra, --enable-all, and HAVE_RPK to determine their specific exposure surface.
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