CVE-2026-0819

Summary

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 Software

Weaknesses

• CWE-121: CWE-121: Stack-based Buffer Overflow
• CWE-787: CWE-787: Out-of-bounds Write

Workarounds

Ensure that applications using wolfSSL PKCS7 signing functionality validate and limit the number of custom signed attributes (signedAttribsSz) to no more than MAX_SIGNED_ATTRIBS_SZ (default 7) minus the number of default signed attributes enabled. Do not allow untrusted input to control the signedAttribs array or its size.

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: total

References

• https://github.com/wolfSSL/wolfssl/pull/9630

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