CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
9.4	$0-$5k	0.00

A vulnerability classified as very critical has been found in libcURL up to 7.50.0 (Network Utility Software). Affected is an unknown part. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Use-after-free vulnerability in libcurl before 7.50.1 allows attackers to control which connection is used or possibly have unspecified other impact via unknown vectors.

The weakness was published 08/03/2016 by Marcelo Echeverria and Fernando Munoz as adv_20160803C as confirmed advisory (Website). The advisory is available at curl.haxx.se. This vulnerability is traded as CVE-2016-5421 since 06/10/2016. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 03/18/2019). The advisory points out:

libcurl works with easy handles using the type 'CURL *' that are objects the application creates using curl_easy_init(). They are the handles that are all each associated with a single transfer at a time. libcurl also has an internal struct that represents and holds most state that is related to a single connection. An easy handle can hold references to one or many such connection structs depending on the requested operations. When using libcurl's multi interface, an application performs transfers by adding one or more easy handles to the multi handle and then it can drive all those transfers in parallel. Due to a flaw, libcurl could leave a pointer to a freed connection struct dangling in an easy handle that was previously added to a multi handle when curl_multi_cleanup() is called with an easy handle still added to it. This does not seem to cause any notable harm if the handle is then closed properly.

The vulnerability was handled as a non-public zero-day exploit for at least 61 days. During that time the estimated underground price was around $0-$5k. The vulnerability scanner Nessus provides a plugin with the ID 92742 (FreeBSD : Vulnerabilities in Curl (e4bc70fc-5a2f-11e6-a1bc-589cfc0654e1)), 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 175804 (Debian Security Update for curl (DSA 3638-1)). The advisory illustrates:

This flaw can also be exploited using libcurl bindings in other languages.

Upgrading to version 7.50.1 eliminates this vulnerability. A possible mitigation has been published immediately after the disclosure of the vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (92742). Similar entries are available at 90448, 90449, 94365 and 95213.

Productinfo

Type

• Network Utility Software

Name

• libcURL

Version

• 7.0
• 7.1
• 7.2
• 7.3
• 7.4
• 7.5
• 7.6
• 7.7
• 7.8
• 7.9
• 7.10
• 7.11
• 7.12
• 7.13
• 7.14
• 7.15
• 7.16
• 7.17
• 7.18
• 7.19
• 7.20
• 7.21
• 7.22
• 7.23
• 7.24
• 7.25
• 7.26
• 7.27
• 7.28
• 7.29
• 7.30
• 7.31
• 7.32
• 7.33
• 7.34
• 7.35
• 7.36
• 7.37
• 7.38
• 7.39
• 7.40
• 7.41
• 7.42
• 7.43
• 7.44
• 7.45
• 7.46
• 7.47
• 7.48
• 7.49
• 7.50

License

• open-source

CPE 2.3info

• 🔍
• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍
• 🔍

CVSSv4info

VulDB CVSS-B Score: 🔍
VulDB CVSS-BT Score: 🔍
VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 9.8
VulDB Meta Temp Score: 9.6

VulDB Base Score: 9.8
VulDB Temp Score: 9.4
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 9.8
NVD Vector: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
unlock	unlock	unlock	unlock	unlock	unlock
unlock	unlock	unlock	unlock	unlock	unlock
unlock	unlock	unlock	unlock	unlock	unlock

VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
ATT&CK: Unknown

Local: No
Remote: Yes

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-Day	unlock	unlock	unlock	unlock
Today	unlock	unlock	unlock	unlock

Nessus ID: 92742
Nessus Name: FreeBSD : Vulnerabilities in Curl (e4bc70fc-5a2f-11e6-a1bc-589cfc0654e1)
Nessus File: 🔍
Nessus Risk: 🔍
Nessus Family: 🔍
Nessus Context: 🔍

OpenVAS ID: 14611
OpenVAS Name: Amazon Linux Local Check: alas-2016-730
OpenVAS File: 🔍
OpenVAS Family: 🔍

Qualys ID: 🔍
Qualys Name: 🔍

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

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

Upgrade: libcURL 7.50.1

Timelineinfo

06/03/2016 🔍
06/10/2016 +7 days 🔍
08/03/2016 +54 days 🔍
08/03/2016 +0 days 🔍
08/03/2016 +0 days 🔍
08/04/2016 +1 days 🔍
08/04/2016 +0 days 🔍
08/05/2016 +1 days 🔍
08/10/2016 +5 days 🔍
03/18/2019 +950 days 🔍

Sourcesinfo

Advisory: adv_20160803C
Researcher: Marcelo Echeverria, Fernando Munoz
Status: Confirmed
Confirmation: 🔍

CVE: CVE-2016-5421 (🔍)
OVAL: 🔍

SecurityTracker: 1036536
SecurityFocus: 92306 - cURL/libcurl CVE-2016-5421 Local Use After Free Denial of Service Vulnerability

See also: 🔍

Entryinfo

Created: 08/04/2016 12:48
Updated: 03/18/2019 20:10
Changes: 08/04/2016 12:48 (65), 03/18/2019 20:10 (25)
Complete: 🔍

Discussion

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