CVE-2026-5504 PKCS7 CBC Padding Oracle — Plaintext Recovery
An attacker can recover plaintext from PKCS7 CBC encrypted data in wolfSSL by exploiting a padding oracle vulnerability due to missing interior padding validation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-5504?
CVE-2026-5504 is a medium-severity vulnerability in Wolfssl Wolfssl, published on 9 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-354
Which versions are affected by CVE-2026-5504?
It affects 1 product.
Products include Wolfssl Wolfssl.
How do I fix CVE-2026-5504?
Upgrade to a fixed version.
Is CVE-2026-5504 being exploited?
There is no known exploitation of CVE-2026-5504 in the wild and no public exploit code.
Other vulnerabilities in Wolfssl Wolfssl
Sources
Also known as DEBIAN-CVE-2026-5504, GHSA-qvjw-73xm-jw34, JLSEC-2026-732, UBUNTU-CVE-2026-5504.