# CVE-2026-6681: wolfSSL out-of-bounds write in PKCS#7 decoding

Source: https://junglewise.ai/threats/cve-2026-6681-wolfssl-out-of-bounds-write-in-pkcs-7-decoding  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-25. Updated: 2026-06-25  
License: CC BY 4.0 with a link back

CVE-2026-6681 · Severity: info · CVSS 1 · Published 2026-06-25

wolfSSL is a security library used to encrypt data for embedded devices and cloud applications. A flaw in how the library handles certain encrypted messages (PKCS#7) allows data to be written into memory areas where it does not belong. While rated as low severity, this could potentially lead to memory corruption or application instability when processing specially formatted security data.

Technologies: [Wolfssl](https://junglewise.ai/threats/technologies/wolfssl). Vendors: [Wolfssl](https://junglewise.ai/threats/vendors/wolfssl).

## Quick answers

**Is CVE-2026-6681 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-6681 being exploited in the wild.

**How severe is CVE-2026-6681?** Informational severity, with a CVSS score of 1, published 25 June 2026.

**Which products and versions are affected?** Wolfssl 3.10.0 to 5.9.0.

**Is there a fix for CVE-2026-6681?** A patch was published on 2026-04-07: Fix merged into master branch via PR 10116 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-6681 attacked?** It is attacked over the network or from the adjacent network, in a software library.

**Am I affected by CVE-2026-6681?** Check whether you run Wolfssl at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An out-of-bounds write vulnerability exists in wolfSSL's PKCS#7 decoding implementation (CWE-787, CWE-120). The root cause is that the decoding path fails to validate the decoded content length against the caller-supplied 'outputSz' buffer size parameter. An attacker providing a crafted PKCS#7 message could cause the library to write decoded data past the end of the allocated buffer. This affects wolfSSL versions 5.9.0 and earlier; the issue was addressed in version 5.9.1.

## Affected products

- wolfSSL wolfSSL 3.10.0 to 5.9.0

## Timeline

- 2026-06-25: disclosed: CVE published to NVD
- 2026-04-07: patched: Fix merged into master branch via PR 10116

## References

- [https://github.com/wolfSSL/wolfssl](https://github.com/wolfSSL/wolfssl)
- [https://github.com/wolfSSL/wolfssl/pull/10116](https://github.com/wolfSSL/wolfssl/pull/10116)
- [https://www.wolfssl.com/docs/security-vulnerabilities/](https://www.wolfssl.com/docs/security-vulnerabilities/)

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