Vulnerability · Published Apr 9, 2026 · Assigned by wolfSSL
CVE-2026-5504PKCS7 CBC Padding Oracle — Plaintext Recovery
Medium 6.3
In plain English
A medium-severity security flaw in wolfSSL from wolfSSL. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 2% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 4.0)6.3Medium
Exploit odds (30 days)0.1%top 98.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.23 | wolfssl | 5.9.1-r0 | ALPINE-CVE-2026-5504 |
| Alpine:v3.24 | wolfssl | 5.9.1-r0 | ALPINE-CVE-2026-5504 |
| Debian:12 | wolfssl | no fix listed | DEBIAN-CVE-2026-5504 |
| Debian:13 | wolfssl | no fix listed | DEBIAN-CVE-2026-5504 |
| Ubuntu:22.04:LTS | wolfssl | no fix listed | UBUNTU-CVE-2026-5504 |
| Ubuntu:24.04:LTS | wolfssl | no fix listed | UBUNTU-CVE-2026-5504 |
| Ubuntu:25.10 | wolfssl | no fix listed | UBUNTU-CVE-2026-5504 |
| Ubuntu:26.04:LTS | wolfssl | no fix listed | UBUNTU-CVE-2026-5504 |
| Ubuntu:26.10 | wolfssl | no fix listed | UBUNTU-CVE-2026-5504 |
Affected products (as reported)
Weakness: CWE-354 · 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