wolfSSL up to 5.9.0 wolfcrypt/src/asn.c DecodeObjectId heap-based overflow

Summaryinfo

A vulnerability was found in wolfSSL up to 5.9.0. It has been classified as critical. This affects the function DecodeObjectId of the file wolfcrypt/src/asn.c. This manipulation causes heap-based overflow. This vulnerability appears as CVE-2026-5187. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability has been found in wolfSSL up to 5.9.0 and classified as critical. Affected by this vulnerability is the function DecodeObjectId of the file wolfcrypt/src/asn.c. The manipulation with an unknown input leads to a heap-based overflow vulnerability. The CWE definition for the vulnerability is CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

Two potential heap out-of-bounds write locations existed in DecodeObjectId() in wolfcrypt/src/asn.c. First, a bounds check only validates one available slot before writing two OID arc values (out[0] and out[1]), enabling a 2-byte out-of-bounds write when outSz equals 1. Second, multiple callers pass sizeof(decOid) (64 bytes on 64-bit platforms) instead of the element count MAX_OID_SZ (32), causing the function to accept crafted OIDs with 33 or more arcs that write past the end of the allocated buffer.

The weakness was presented by ytsun. This vulnerability is known as CVE-2026-5187 since 03/30/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 04/12/2026).

The vulnerability scanner Nessus provides a plugin with the ID 305890 (Linux Distros Unpatched Vulnerability : CVE-2026-5187), which helps to determine the existence of the flaw in a target environment.

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

The vulnerability is also documented in the vulnerability database at Tenable (305890). 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

CPE 2.3info

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CPE 2.2info

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

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