wolfSSL up to 5.9.0 Authentication Tag ssl_DecodePacket integer underflow

Summaryinfo

A vulnerability, which was classified as problematic, has been found in wolfSSL up to 5.9.0. Affected by this vulnerability is the function ssl_DecodePacket of the component Authentication Tag Handler. Performing a manipulation results in integer underflow. This vulnerability was named CVE-2026-5778. The attack may be initiated remotely. There is no available exploit. To fix this issue, it is recommended to deploy a patch.

Detailsinfo

A vulnerability, which was classified as problematic, was found in wolfSSL up to 5.9.0. This affects the function ssl_DecodePacket of the component Authentication Tag Handler. The manipulation with an unknown input leads to a integer underflow vulnerability. CWE is classifying the issue as 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. This is going to have an impact on availability. The summary by CVE is:

Integer underflow in wolfSSL packet sniffer <= 5.9.0 allows an attacker to cause a program crash in the AEAD decryption path by injecting a TLS record shorter than the explicit IV plus authentication tag into traffic inspected by ssl_DecodePacket. The underflow wraps a 16-bit length to a large value that is passed to AEAD decryption routines, causing a large out-of-bounds read and crash. An unauthenticated attacker can trigger this remotely via malformed TLS Application Data records.

The weakness was presented by Zou Dikai. It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-5778 since 04/08/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 305881 (Linux Distros Unpatched Vulnerability : CVE-2026-5778), which helps to determine the existence of the flaw in a target environment.

Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com.

The vulnerability is also documented in the vulnerability database at Tenable (305881). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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