Medium severity · published Apr 9, 2026
CVE-2026-5504
PKCS7 CBC Padding Oracle — Plaintext Recovery
5.3
CVSS
0.1%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.1% · higher than 1% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
WO
wolfSSL · wolfSSL
through 5.9.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-5504
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-5504
Issue Tracking
https://github.com/wolfSSL/wolfssl/pull/10088
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