CVE Intelligence
Critical Cryptography

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

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.

Published Sep 5, 2006 · Updated Oct 30, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: redhat

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 5.1% (30-day exploitation probability)+14
  • Technical severity (critical)+10

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
5.09%
ahead of 92% of scored CVEs · Oct 30, 2026
Affects
Openssl
Openssl and 6 more
CVSS base
9.1
Critical · 3 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Openssl Openssl, Red Hat Red Hat Enterprise Linux 3, Red Hat Red Hat Enterprise Linux 4…).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. Apply the fixed version or the patch documented under Remediation.
  4. EPSS ahead of 92% of scored CVEs: prioritize it in the patch queue.
  5. Search available logs for exploit probes matching the vulnerability class (cryptography), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Openssl Openssl version 0.9.7cversion 0.9.6eversion 0.9.6fversion 0.9.6gversion 0.9.6hversion 0.9.6iversion 0.9.6jversion 0.9.6k
and 37 more version 0.9.6lversion 0.9.6mversion 0.9.7aversion 0.9.7bversion 0.9.1cversion 0.9.7dversion 0.9.7eversion 0.9.7fversion 0.9.7gversion 0.9.7hversion 0.9.7iversion 0.9.7jversion 0.9.8version 0.9.8aversion 0.9.8bversion 0.9.6c≤ 0.9.7version 0.9.2bversion 0.9.3version 0.9.3aversion 0.9.4version 0.9.5version 0.9.5-beta1version 0.9.5-beta2version 0.9.5aversion 0.9.5a-beta1version 0.9.6version 0.9.6dversion 0.9.6bversion 0.9.6a-beta3version 0.9.6a-beta2version 0.9.6a-beta1version 0.9.6aversion 0.9.6-beta3version 0.9.6-beta2version 0.9.6-beta1version 0.9.5a-beta2
Vulnerable NIST National Vulnerability Database
Red Hat Red Hat Enterprise Linux 3 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat Enterprise Linux 4 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat Network Satellite Server v 4.2 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat Network Satellite Server v 4.2 (RHEL3) versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat Network Satellite Server v 5.0 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat Network Satellite Server v 5.1 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
9.1 CVSS 3.1 Critical 3.9 5.2 secalert@redhat.com via NIST National Vulnerability Database
9.1 CVSS 3.1 Critical — — redhat via CVE Program (cve.org) e CISA ADP
4.3 CVSS 2.0 Medium 8.6 2.9 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N (score shown at the top: secalert@redhat.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-347 · Improper Verification of Cryptographic Signature

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Check TLS negotiations and unexpected certificates in the component’s traffic.
web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · red hat/red hat enterprise linux 3, red hat/red hat enterprise linux 4, red hat/red hat network satellite server v 4.2,
    Oct 30, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 30, 2026
  • Fix documented
    Oct 30, 2026 · NIST National Vulnerability Database
  • Affected products added · openssl/openssl
    Oct 30, 2026 · NIST National Vulnerability Database
  • CVSS changed · 9.1
    Oct 30, 2026 · NIST National Vulnerability Database
  • Source status changed · → Modified
    Oct 30, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 30, 2026 · Alertas do Telegram
  • 2006
  • CVE published
    Sep 5, 2006 · redhat

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 30, 2026 – Oct 30, 2026
  • 1× Official description updated · Oct 30, 2026 – Oct 30, 2026

References

100 on the record

Elsewhere on this site

Openssl
every CVE for this vendor
Cryptography
same class
CWE-347
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-84783 Use-After-Free in X.509 Extension Cache Under Concurrent Use Sep 29, 2026
  • CVE-2026-84784 QUIC: Unbounded RETIRE_CONNECTION_ID Backlog Sep 29, 2026
  • CVE-2026-84782 DTLS Retransmits Handshake Messages From a Stale Buffer Offset Sep 29, 2026
  • CVE-2026-75805 NULL Pointer Dereference in CMP Client Revocation Response Handling Sep 29, 2026
  • CVE-2026-75806 Unauthenticated and Undersized DTLS 1.2 AEAD Record Causes DoS Sep 29, 2026
  • CVE-2026-77696 Timing Side-Channel in SM2 Signature Generation Sep 29, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No CISA SSVC assessment.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2006-4339 is "Openssl: openssl: signature forgery via improper pkcs-1 padding removal leading to certificate validation bypass", rated Critical. It affects Openssl (Openssl); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.1 describes technical severity. EPSS 5.09% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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