What’s Vulnerable › Vulnerabilities
CVE-2026-0819: Stack buffer overflow in PKCS7 SignedData encoding with custom signed attributes
- Severity: high (CVSS 7.1 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.1% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-03-19 · updated 2026-06-17
- Weakness: CWE-121
Description
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.
Affected products
- wolfSSL: from 5.5.0 before 5.9.0 — fixed in 5.9.0
How to fix
Upgrade to a fixed version: wolfSSL 5.9.0. Check the vendor advisory for mitigations.
References
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