CVE-2006-4339: Openssl: openssl: signature forgery via improper pkcs-1 padding removal leading to certificate validation bypass

Severity: medium (CVSS 4.3 v2.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 5.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2006-09-05 · updated 2026-10-30
Weakness: CWE-347

Description

A flaw was found in OpenSSL. When configured to use an RSA key with exponent 3, OpenSSL improperly removes PKCS-1 padding before generating a hash. This allows remote attackers to forge PKCS #1 v1.5 signatures. Consequently, OpenSSL may incorrectly verify X.509 and other certificates, leading to a bypass of trust and authentication mechanisms.

Affected products

OpenSSL: through 0.9.7; 0.9.1c, 0.9.2b, 0.9.3, 0.9.3a, 0.9.4, 0.9.5 (+38)
Red Hat Enterprise Linux 3: all versions — fixed in 0:0.9.7a-33.18
Red Hat Enterprise Linux 4: all versions — fixed in 0:0.9.7a-43.11
Red Hat Network Satellite Server v 4.2: all versions — fixed in 0:5.0.2-3
Red Hat Network Satellite Server v 4.2 (RHEL3): all versions — fixed in 0:5.0.2-3
Red Hat Network Satellite Server v 5.0: all versions — fixed in 0:5.0.2-3
Red Hat Network Satellite Server v 5.1: all versions — fixed in 0:5.1.1-3

How to fix

Upgrade to a fixed version: Red Hat Enterprise Linux 3 0:0.9.7a-33.18; Red Hat Enterprise Linux 4 0:0.9.7a-43.11; Red Hat Network Satellite Server v 4.2 0:5.0.2-3; Red Hat Network Satellite Server v 4.2 (RHEL3) 0:5.0.2-3; Red Hat Network Satellite Server v 5.0 0:5.0.2-3; Red Hat Network Satellite Server v 5.1 0:5.1.1-3. Check the vendor advisory for mitigations.

References

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