wolfSSL up to 5.9.0 Certificate integer underflow

Summaryinfo

A vulnerability was found in wolfSSL up to 5.9.0 and classified as critical. This affects an unknown part of the component Certificate Handler. Executing a manipulation can lead to integer underflow. This vulnerability is registered as CVE-2026-5188. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability has been found in wolfSSL up to 5.9.0 and classified as critical. This vulnerability affects an unknown code of the component Certificate Handler. The manipulation with an unknown input leads to a integer underflow vulnerability. The CWE definition for the vulnerability is CWE-191. The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.

The weakness was published by Muhammad Arya Arjuna Habibullah. The advisory is available at github.com. This vulnerability was named CVE-2026-5188 since 03/30/2026. The exploitation appears to be difficult. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 04/10/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Name

• wolfSSL

Version

• 5.0
• 5.1
• 5.2
• 5.3
• 5.4
• 5.5
• 5.6
• 5.7
• 5.8
• 5.9.0

License

• open-source

Website

• Product: https://github.com/wolfSSL/wolfssl/

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