CVE-2026-5504 PUBLISHED

PKCS7 CBC Padding Oracle — Plaintext Recovery

Assigner: wolfSSL
Reserved: 03.04.2026 Published: 09.04.2026 Updated: 09.04.2026

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover plaintext through repeated decryption queries with modified ciphertext. In previous versions of wolfSSL the interior padding bytes are not validated.

Metrics

CVSS 4.0

CVSS Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
CVSS Score: 6.3

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	Low	Confidentiality	None
Attack Complexity	High	Integrity	None	Integrity	None
Attack Requirements	Present	Availability	None	Availability	None
Privileges Required	None
User Interaction	None

CVSS 4.0

Product Status

Vendor	wolfSSL
Product	wolfSSL
Versions	Default: unaffected affected from 0 to 5.9.0 (incl.)

Credits

Sunwoo Lee of Korea Institute of Energy Technology (KENTECH) for the report. finder
Woohyun Choi of Korea Institute of Energy Technology (KENTECH) for the report. finder
Seunghyun Yoon of Korea Institute of Energy Technology (KENTECH) for the report. finder

References

https://github.com/wolfSSL/wolfssl/pull/10088

Problem Types

CWE-354 Improper validation of integrity check value CWE

Impacts

CAPEC-463 Padding Oracle Crypto Attack