OpenSSL 1.0.1n/1.0.1o/1.0.2b/1.0.2c x509 Basic Constraints crypto/x509/x509_vfy.c X509_verify_cert 7pk security

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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A vulnerability was found in OpenSSL 1.0.1n/1.0.1o/1.0.2b/1.0.2c (Network Encryption Software). It has been declared as critical. This vulnerability affects the function X509_verify_cert of the file crypto/x509/x509_vfy.c of the component x509 Basic Constraints Handler. The manipulation with an unknown input leads to a 7pk security vulnerability. The CWE definition for the vulnerability is CWE-254. As an impact it is known to affect confidentiality, integrity, and availability.

The issue has been introduced in 06/11/2015. The weakness was shared 07/09/2015 with Oracle as confirmed git commit (GIT Repository). The advisory is available at This vulnerability was named CVE-2015-1793 since 02/17/2015. The exploitation appears to be difficult. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details and also a public exploit are known. This vulnerability is assigned to T1211 by the MITRE ATT&CK project. Responsible for the vulnerability is the following code:


It is possible to download the exploit at It is declared as highly functional. The vulnerability was handled as a non-public zero-day exploit for at least 28 days. During that time the estimated underground price was around $25k-$100k. The vulnerability scanner Nessus provides a plugin with the ID 84647 (Amazon Linux AMI : openssl (ALAS-2015-564)), which helps to determine the existence of the flaw in a target environment. It is assigned to the family Amazon Linux Local Security Checks and running in the context l. The commercial vulnerability scanner Qualys is able to test this issue with plugin 86487 (HP System Management Homepage Multiple Vulnerabilities (HPSBMU03546)).

Upgrading to version 1.0.1p or 1.0.2d eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at The problem might be mitigated by replacing the product with BoringSSL as an alternative. The best possible mitigation is suggested to be upgrading to the latest version. A possible mitigation has been published before and not just after the disclosure of the vulnerability. The vulnerability will be addressed with the following lines of code:

ctx->last_untrusted = sk_X509_num(ctx->chain);
Furthermore it is possible to detect and prevent this kind of attack with TippingPoint and the filter 20122.

The vulnerability is also documented in the databases at X-Force (104500), Tenable (84647) and Exploit-DB (38640). The entries 78584, 78603, 78601 and 78562 are related to this item.







  • end of life (old version)

CPE 2.3info

CPE 2.2info


VulDB Meta Base Score: 6.5
VulDB Meta Temp Score: 6.1

VulDB Base Score: 6.5
VulDB Temp Score: 5.7
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 6.5
NVD Vector: 🔍



VulDB Base Score: 🔍
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Class: 7pk security
CWE: CWE-254
ATT&CK: T1211

Local: No
Remote: Yes

Availability: 🔍
Access: Public
Status: Highly functional
Download: 🔍

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍


Nessus ID: 84647
Nessus Name: Amazon Linux AMI : openssl (ALAS-2015-564)
Nessus File: 🔍
Nessus Risk: 🔍
Nessus Family: 🔍
Nessus Context: 🔍

OpenVAS ID: 14611
OpenVAS Name: Amazon Linux Local Check: ALAS-2015-564
OpenVAS File: 🔍
OpenVAS Family: 🔍

Qualys ID: 🔍
Qualys Name: 🔍

MetaSploit ID: openssl_altchainsforgery_mitm_proxy.rb
MetaSploit Name: OpenSSL Alternative Chains Certificate Forgery MITM Proxy
MetaSploit File: 🔍

Exploit-DB: 🔍

Threat Intelligenceinfo

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


Recommended: Upgrade
Status: 🔍

0-Day Time: 🔍

Upgrade: OpenSSL 1.0.1p/1.0.2d
Patch: 9a0db453ba017ebcaccbee933ee6511a9ae4d1c8
Alternative: BoringSSL
TippingPoint: 🔍

McAfee IPS: 🔍
McAfee IPS Version: 🔍


02/17/2015 🔍
06/11/2015 +114 days 🔍
07/09/2015 +27 days 🔍
07/09/2015 +0 days 🔍
07/09/2015 +0 days 🔍
07/09/2015 +0 days 🔍
07/10/2015 +1 days 🔍
07/13/2015 +2 days 🔍
08/17/2015 +35 days 🔍
07/15/2016 +333 days 🔍
05/23/2022 +2138 days 🔍



Organization: Oracle
Status: Confirmed
Confirmation: 🔍

CVE: CVE-2015-1793 (🔍)

X-Force: 104500 - OpenSSL certificate chain logic security bypass
SecurityTracker: 1032817
Vulnerability Center: 52055 - OpenSSL Remote Bypass Restrictions via Untrusted Certificates, Medium
SecurityFocus: 91787 - Oracle July 2016 Critical Patch Update Multiple Vulnerabilities

scip Labs:
See also: 🔍


Created: 07/10/2015 09:36 AM
Updated: 05/23/2022 06:57 PM
Changes: 07/10/2015 09:36 AM (71), 09/21/2018 10:28 AM (32), 05/23/2022 06:49 PM (4), 05/23/2022 06:57 PM (10)
Complete: 🔍


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