CVE-2006-4339: A flaw was found in OpenSSL

Q: How do I fix CVE-2006-4339?

openssl: upgrade to newer than 0.9.7. Exact commands for each OS are on this page.

Q: Is CVE-2006-4339 being exploited?

CVE-2006-4339 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2006-4339 affect?

CVE-2006-4339 affects openssl. Severity is critical (CVSS 9.1). 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 inc

Q: How urgent is CVE-2006-4339?

Priority 65/100. Critical severity; EPSS top 8%: very likely to be exploited; Remotely exploitable, no login, no user action; On your watchlist

This week

CRITICAL 9.1REMOTEWATCHLISTUPGRADE

CVE-2006-4339 is a critical-severity flaw (CVSS 9.1) affecting openssl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Critical severity
EPSS top 8%: very likely to be exploited
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	5.1% (top 8%)
CISA exploited list	No
Weakness	CWE-347, CWE-310
Published	2006-09-05
Last modified	2026-10-30

Publisher (CNA): Red Hat, Inc. · Vendor: openssl

Last updated 2026-10-30 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2006-09-05 17:04 UTCPublished CVE record published
2026-10-30 17:17 UTCUpdated Record last modified

openssl openssl UPGRADE

Affected: <= 0.9.7 · 0.9.1c · 0.9.2b · 0.9.3 · 0.9.3a · 0.9.4 · 0.9.5 · 0.9.5 beta1

Fixed in: newer than 0.9.7

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy openssl || rpm -q openssl || openssl --version

2. UPGRADE to newer than 0.9.7 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade openssl

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade openssl

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2006-4339?

openssl: upgrade to newer than 0.9.7. Exact commands for each OS are on this page.

Is CVE-2006-4339 being exploited?

CVE-2006-4339 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2006-4339 affect?

CVE-2006-4339 affects openssl. Severity is critical (CVSS 9.1). 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 inc

How urgent is CVE-2006-4339?

Priority 65/100. Critical severity; EPSS top 8%: very likely to be exploited; Remotely exploitable, no login, no user action; On your watchlist

Software pages

OpenSSL vulnerabilities

Related CVEs

CVE-2025-15467 HIGH 8.8 UPGRADE Issue summary: Parsing CMS AuthEnvelopedData or EnvelopedData message with maliciously crafted AEAD parameters
CVE-2024-0727 MEDIUM 5.5 UPGRADE Issue summary: Processing a maliciously formatted PKCS12 file may lead OpenSSL to crash leading to a potential
CVE-2023-6129 MEDIUM 6.5 UPGRADE Issue summary: The POLY1305 MAC (message authentication code) implementation contains a bug that might corrupt
CVE-2023-5678 MEDIUM 5.3 UPGRADE Issue summary: Generating excessively long X9.42 DH keys or checking excessively long X9.42 DH keys or paramet
CVE-2023-4807 HIGH 7.8 UPGRADE Issue summary: The POLY1305 MAC (message authentication code) implementation contains a bug that might corrupt

References

← Back to latest CVEs