Contents
- Vital information on this issue
- Scanning For and Finding Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration
- Penetration Testing (Pentest) for this Vulnerability
- Security updates on Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration
- Disclosures related to Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration
- Confirming the Presence of Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration
- False positive/negatives
- Patching/Repairing this vulnerability
- Exploits related to Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration
Vital Information on This Issue
Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration is a Medium risk vulnerability that is one of the most frequently found on networks around the world. This issue has been around since at least 1990 but has proven either difficult to detect, difficult to resolve or prone to being overlooked entirely.
| Vulnerability Name: | OpenSSH S/KEY Authentication Account Enumeration |
|---|---|
| Test ID: | 14020 |
| Risk: | Medium |
| Category: | SSH servers |
| Type: | Attack |
| Summary: | OpenSSH 4.6 and earlier, when ChallengeResponseAuthentication is enabled, allows remote attackers to determine the existence of user accounts by attempting to authenticate via S/KEY, which displays a different response if the user account exists, a similar issue to CVE-2001-1483. $OUTPUT |
| Impact: | Allows remote attackers to determine the existence of user accounts. |
| Solution: | A patch currently does not exist for this issue. As a workaround, either set ‘ChallengeResponseAuthentication’ in the OpenSSH config to ‘no’ or use a version of OpenSSH without S/KEY support compiled in. |
| CVE: | CVE-2007-2243 |
| More Information: | http://cxsecurity.com/issue/WLB-2007040138https://exchange.xforce.ibmcloud.com/vulnerabilities/33794 |
| Nist NVD (CVSS): | AV:N/AC:L/Au:N/C:P/I:N/A:N) |
| CVSS Score: |
Scanning For and Finding Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration
Use of Vulnerability Management tools, like AVDS, are standard practice for the discovery of this vulnerability. The primary failure of VA in finding this vulnerability is related to setting the proper scope and frequency of network scans. It is vital that the broadest range of hosts (active IPs) possible are scanned and that scanning is done frequently. We recommend weekly. Your existing scanning solution or set of test tools should make this not just possible, but easy and affordable. If that is not the case, please consider AVDS.
Penetration Testing (pentest) for this Vulnerability
The Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration is prone to false positive reports by most vulnerability assessment solutions. AVDS is alone in using behavior based testing that eliminates this issue. For all other VA tools security consultants will recommend confirmation by direct observation. In any case Penetration testing procedures for discovery of Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration produces the highest discovery accuracy rate, but the infrequency of this expensive form of testing degrades its value. The ideal would be to have pentesting accuracy and the frequency and scope possibilities of VA solutions, and this is accomplished only by AVDS.
Security Updates on Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration
Given that this is one of the most frequently found vulnerabilities, there is ample information regarding mitigation online and very good reason to get it fixed. Hackers are also aware that this is a frequently found vulnerability and so its discovery and repair is that much more important. It is so well known and common that any network that has it present and unmitigated indicates “low hanging fruit” to attackers.
Disclosures related to this vulnerability
http://lists.grok.org.uk/pipermail/full-disclosure/2007-April/053906.html
http://www.securityfocus.com/bid/23601
Confirming the Presence of Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration
AVDS is currently testing for and finding this vulnerability with zero false positives. If your current set of tools is indicating that it is present but you think it is probably a false positive, please contact us for a demonstration of AVDS.
False positive/negatives
The secret killer of VA solution value is the false positive. There was an industry wide race to find the most vulnerabilities, including Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration ,and this resulted in benefit to poorly written tests that beef up scan reports by adding a high percentage of uncertainty. This may have sold a lot of systems some years ago, but it also stuck almost all VA solutions with deliberately inaccurate reporting that adds time to repairs that no administrator can afford. Beyond Security did not participate in this race to mutually assured destruction of the industry and to this day produces the most accurate and actionable reports available.
Patching/Repairing this Vulnerability
Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration is a Medium risk vulnerability that is also high frequency and high visibility. This is the most severe combination of security factors that exists and it is extremely important to find it on your network and fix it as soon as possible.
Exploits related to Vulnerabilities in OpenSSH S/KEY Authentication Account Enumeration
https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2007-2243
http://seclists.org/fulldisclosure/2007/Apr/589
https://vigilance.fr/vulnerability/OpenSSH-account-enumeration-via-S-Key-6756