OpenSSH 5.6/5.7 Legacy Certificate access control

CVSS Meta Temp Score
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CTI Interest Score
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6.7$0-$5k0.00

Summaryinfo

A vulnerability described as problematic has been identified in OpenSSH 5.6/5.7. This vulnerability affects unknown code of the component Legacy Certificate Handler. Executing a manipulation as part of Legacy Certificate can lead to access control. This vulnerability is tracked as CVE-2011-0539. No exploit exists. A patch should be applied to remediate this issue.

Detailsinfo

A vulnerability was found in OpenSSH 5.6/5.7 (Connectivity Software). It has been declared as critical. This vulnerability affects an unknown code block of the component Legacy Certificate Handler. The manipulation as part of a Legacy Certificate leads to a access control vulnerability. The CWE definition for the vulnerability is CWE-264. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

The key_certify function in usr.bin/ssh/key.c in OpenSSH 5.6 and 5.7, when generating legacy certificates using the -t command-line option in ssh-keygen, does not initialize the nonce field, which might allow remote attackers to obtain sensitive stack memory contents or make it easier to conduct hash collision attacks.

The weakness was disclosed 02/07/2011 by Mateusz Kocielski (Website). The advisory is available at openssh.com. This vulnerability was named CVE-2011-0539 since 01/20/2011. Access to the local network is required for this attack. No form of authentication is required for a successful exploitation. The technical details are unknown and an exploit is not available. This vulnerability is assigned to T1068 by the MITRE ATT&CK project.

The vulnerability scanner Nessus provides a plugin with the ID 51920 (OpenSSH Legacy Certificate Signing Information Disclosure), which helps to determine the existence of the flaw in a target environment. It is assigned to the family Misc. and running in the context r. The commercial vulnerability scanner Qualys is able to test this issue with plugin 216077 (VMware ESXi 5.5.0 Patch Release ESXi550-201501001 Missing (KB2099265)).

Applying a patch is able to eliminate this problem. The bugfix is ready for download at openssh.com. A possible mitigation has been published even before and not after the disclosure of the vulnerability.

The vulnerability is also documented in the databases at X-Force (65163), Tenable (51920), SecurityFocus (BID 46155†), Secunia (SA43181†) and SecurityTracker (ID 1025028†). The entries VDB-55641 and VDB-56678 are pretty similar. If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.9
VulDB Meta Temp Score: 6.7

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
VulDB Vector: 🔍
VulDB Reliability: 🔍

ADP CISA Base Score: 7.5
ADP CISA Vector: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Access control
CWE: CWE-264
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

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Nessus ID: 51920
Nessus Name: OpenSSH Legacy Certificate Signing Information Disclosure
Nessus File: 🔍
Nessus Risk: 🔍
Nessus Family: 🔍
Nessus Context: 🔍

OpenVAS ID: 103064
OpenVAS Name: OpenSSH Legacy Certificate Signing Information Disclosure Vulnerability
OpenVAS File: 🔍
OpenVAS Family: 🔍

Qualys ID: 🔍
Qualys Name: 🔍

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔍

Patch: openssh.com

Timelineinfo

01/20/2011 🔍
02/04/2011 +15 days 🔍
02/04/2011 +0 days 🔍
02/04/2011 +0 days 🔍
02/07/2011 +3 days 🔍
02/09/2011 +2 days 🔍
02/10/2011 +1 days 🔍
02/14/2011 +4 days 🔍
02/15/2011 +1 days 🔍
05/29/2026 +5582 days 🔍

Sourcesinfo

Advisory: openssh.com
Researcher: Mateusz Kocielski
Status: Confirmed
Confirmation: 🔍

CVE: CVE-2011-0539 (🔍)
GCVE (CVE): GCVE-0-2011-0539
GCVE (VulDB): GCVE-100-4282
X-Force: 65163
SecurityFocus: 46155 - OpenSSH Legacy Certificate Signing Information Disclosure Vulnerability
Secunia: 43181 - OpenSSH Two Weaknesses, Not Critical
SecurityTracker: 1025028
Vulnerability Center: 29755 - OpenSSH 5.6 and 5.7 Remote Stack Memory Information Disclosure, Medium

See also: 🔍

Entryinfo

Created: 02/15/2011 16:08
Updated: 05/29/2026 23:40
Changes: 02/15/2011 16:08 (77), 03/15/2017 12:45 (8), 03/18/2021 18:45 (3), 03/18/2021 18:49 (1), 12/01/2024 21:18 (17), 05/29/2026 23:40 (12)
Complete: 🔍
Cache ID: 216::103

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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