CVE-2026-94418 Signature failure masked by date error under WOLFSSL_SMALL_CERT_VERIFY
Attackers can bypass certificate signature verification in wolfSSL when using specific low-resource configurations and date-error overriding callbacks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-94418?
CVE-2026-94418 is a low-severity vulnerability in Wolfssl Wolfssl, published on 27 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Under WOLFSSL_SMALL_CERT_VERIFY, ProcessPeerCertParse() runs the certificate signature check separately from the parse to keep peak memory down, then merges the two results, but it merged the signature result back only when the parse returned 0, so any parse error hid it. ParseCertRelative() reaches its validity-date, name-constraint and critical-extension checks only after ConfirmSignature() has passed, so splitting the signature check out inverts the precedence that makes "override date errors" a sound policy, and ASN_SIG_CONFIRM_E is never surfaced anywhere. The attacker needs no key material from the real PKI and no CA compromise: a self-made certificate carrying the expected subject name, the trusted CA's subject as its issuer, arbitrary bytes where the signature goes, a validity window in the past and the attacker's own key pair is sufficient. Affected builds define WOLFSSL_SMALL_CERT_VERIFY, which is off by default, is not set implicitly by any platform or preset header, and is not reachable from any CMake option; the autotools routes are --enable-lowresource, --enable-leantls, --enable-tinytls13=cert and --enable-tinytls13=mutualauth, and examples/configs/user_settings_embedded.h reaches it through WC_CFG_SMALL_CERT_VERIFY, which ships as 0, while neither --enable-all nor --enable-distro enables it at all. The application must additionally install a verify callback through wolfSSL_CTX_set_verify() or wolfSSL_set_verify() with WOLFSSL_VERIFY_PEER that returns 1 for ASN_BEFORE_DATE_E or ASN_AFTER_DATE_E; wolfSSL ships this exact shape as myVerify() in wolfssl/test.h under VERIFY_OVERRIDE_DATE_ERR, which examples/client -D selects. An application with no callback, or whose callback returns preverify for date errors, still fails the handshake, and wolfSSL_CertManagerVerifyBuffer() and wc_CheckCertSignature() report ASN_SIG_CONFIRM_E correctly in the same binary. TLS 1.2 and TLS 1.3 are affected in both directions, and DTLS reaches the same function; where the forged certificate is a chain certificate the callback's consent causes it to be cached in the WOLFSSL_CTX certificate manager, so an exposed deployment must restart the context or the process rather than merely reconnect.
Weakness: CWE-347
Which versions are affected by CVE-2026-94418?
It affects 1 product.
Products include Wolfssl Wolfssl.
How do I fix CVE-2026-94418?
No fix has been published for CVE-2026-94418 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-94418 being exploited?
There is no known exploitation of CVE-2026-94418 in the wild and no public exploit code.
Other vulnerabilities in Wolfssl Wolfssl
Sources
Also known as AZL-105182, DEBIAN-CVE-2026-94418, GHSA-q4rg-xp99-jj6q, UBUNTU-CVE-2026-94418.