OpenSSL DSA Signing crypto/dsa/dsa_ossl.c information disclosure

CVSS Meta Temp Score
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5.4$0-$5k0.00

Summaryinfo

A vulnerability, which was classified as problematic, has been found in OpenSSL. Affected by this vulnerability is an unknown functionality of the file crypto/dsa/dsa_ossl.c of the component DSA Signing. Performing a manipulation results in information disclosure. This vulnerability is cataloged as CVE-2016-2178. The attack must be initiated from a local position. There is no exploit available. It is recommended to apply a patch to fix this issue.

Detailsinfo

A vulnerability, which was classified as problematic, was found in OpenSSL (Network Encryption Software). This affects an unknown functionality of the file crypto/dsa/dsa_ossl.c of the component DSA Signing. The manipulation with an unknown input leads to a information disclosure vulnerability. CWE is classifying the issue as CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. This is going to have an impact on confidentiality. The summary by CVE is:

The dsa_sign_setup function in crypto/dsa/dsa_ossl.c in OpenSSL through 1.0.2h does not properly ensure the use of constant-time operations, which makes it easier for local users to discover a DSA private key via a timing side-channel attack.

The weakness was shared 05/23/2016 as Make Sure DSA Signing Exponentiations Really are Constant-Time as confirmed paper (Website). It is possible to read the advisory at eprint.iacr.org. This vulnerability is uniquely identified as CVE-2016-2178 since 01/29/2016. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1592 according to MITRE ATT&CK. The advisory points out:

Operations in the DSA signing algorithm should run in constant time in order to avoid side channel attacks. A flaw in the OpenSSL DSA implementation means that a non-constant time codepath is followed for certain operations. This has been demonstrated through a cache-timing attack to be sufficient for an attacker to recover the private DSA key.

The vulnerability scanner Nessus provides a plugin with the ID 91553 (FreeBSD : OpenSSL -- vulnerability in DSA signing (6f0529e2-2e82-11e6-b2ec-b499baebfeaf)), which helps to determine the existence of the flaw in a target environment. It is assigned to the family FreeBSD Local Security Checks and running in the context l. The commercial vulnerability scanner Qualys is able to test this issue with plugin 316384 (Cisco Unity Express OpenSSL Multiple Vulnerabilities (cisco-sa-20160927-openssl)).

Applying a patch is able to eliminate this problem. The bugfix is ready for download at git.openssl.org. A possible mitigation has been published immediately after the disclosure of the vulnerability. The vulnerability will be addressed with the following lines of code:

if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
   BN_set_flags(K, BN_FLG_CONSTTIME);
}

The vulnerability is also documented in the databases at Tenable (91553), SecurityFocus (BID 91081†) and SecurityTracker (ID 1036054†). Further details are available at openbsd.org. The entries VDB-88080, VDB-90396, VDB-90937 and VDB-90940 are related to this item. Be aware that VulDB is the high quality source for vulnerability data.

Affected

  • Cisco Products
  • OpenSSL
  • OpenBSD

Productinfo

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Name

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.5
VulDB Meta Temp Score: 5.4

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD 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: Information disclosure
CWE: CWE-200 / CWE-284 / CWE-266
CAPEC: 🔍
ATT&CK: 🔍

Physical: Partially
Local: Yes
Remote: Yes

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

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Nessus ID: 91553
Nessus Name: FreeBSD : OpenSSL -- vulnerability in DSA signing (6f0529e2-2e82-11e6-b2ec-b499baebfeaf)
Nessus File: 🔍
Nessus Risk: 🔍
Nessus Family: 🔍
Nessus Context: 🔍

OpenVAS ID: 862884
OpenVAS Name: OpenSSL Multiple Vulnerabilities -19 Jun16 (Windows)
OpenVAS File: 🔍
OpenVAS Family: 🔍

Qualys ID: 🔍
Qualys Name: 🔍

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Patch
Status: 🔍

Reaction Time: 🔍
0-Day Time: 🔍
Exposure Time: 🔍

Patch: 399944622df7bd81af62e67ea967c470534090e2

Timelineinfo

01/29/2016 🔍
05/23/2016 +115 days 🔍
05/23/2016 +0 days 🔍
06/08/2016 +16 days 🔍
06/08/2016 +0 days 🔍
06/10/2016 +2 days 🔍
06/13/2016 +3 days 🔍
06/19/2016 +6 days 🔍
08/23/2022 +2256 days 🔍

Sourcesinfo

Product: openssl.org

Advisory: Make Sure DSA Signing Exponentiations Really are Constant-Time
Status: Confirmed
Confirmation: 🔍

CVE: CVE-2016-2178 (🔍)
GCVE (CVE): GCVE-0-2016-2178
GCVE (VulDB): GCVE-100-87879

OVAL: 🔍

SecurityFocus: 91081 - OpenSSL CVE-2016-2178 Side Channel Attack Information Disclosure Vulnerability
SecurityTracker: 1036054

Misc.: 🔍
See also: 🔍

Entryinfo

Created: 06/13/2016 11:54
Updated: 08/23/2022 12:25
Changes: 06/13/2016 11:54 (81), 06/24/2019 12:23 (12), 08/23/2022 12:25 (3)
Complete: 🔍
Cache ID: 216::103

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