wolfSSL up to 5.8.x wc_PKCS7_BuildSignedAttributes capacity stack-based overflow

Summaryinfo

A vulnerability labeled as critical has been found in wolfSSL up to 5.8.x. The impacted element is the function wc_PKCS7_BuildSignedAttributes. The manipulation of the argument capacity results in stack-based overflow. This vulnerability is reported as CVE-2026-0819. The attack can be launched remotely. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as critical, was found in wolfSSL up to 5.8.x. Affected is the function wc_PKCS7_BuildSignedAttributes. The manipulation of the argument capacity with an unknown input leads to a stack-based overflow vulnerability. CWE is classifying the issue as CWE-121. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

A stack buffer overflow vulnerability exists in wolfSSL's PKCS7 SignedData encoding functionality. In wc_PKCS7_BuildSignedAttributes(), when adding custom signed attributes, the code passes an incorrect capacity value (esd->signedAttribsCount) to EncodeAttributes() instead of the remaining available space in the fixed-size signedAttribs[7] array. When an application sets pkcs7->signedAttribsSz to a value greater than MAX_SIGNED_ATTRIBS_SZ (default 7) minus the number of default attributes already added, EncodeAttributes() writes beyond the array bounds, causing stack memory corruption. In WOLFSSL_SMALL_STACK builds, this becomes heap corruption. Exploitation requires an application that allows untrusted input to control the signedAttribs array size when calling wc_PKCS7_EncodeSignedData() or related signing functions.

The weakness was disclosed by Maor Caplan. The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-0819 since 01/09/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 303263 (Linux Distros Unpatched Vulnerability : CVE-2026-0819), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.9.0 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (303263) and EUVD (EUVD-2026-13131). Once again VulDB remains the best source 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

License

• open-source

Website

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

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Once again VulDB remains the best source for vulnerability data.

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