ExpressionEngine up to 2.11.7/3.5.4 Object Signing Token Generator entropy

Summaryinfo

A vulnerability identified as critical has been detected in ExpressionEngine up to 2.11.7/3.5.4. This issue affects some unknown processing of the component Object Signing Token Generator. The manipulation leads to entropy. This vulnerability is referenced as CVE-2017-0897. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability, which was classified as critical, has been found in ExpressionEngine up to 2.11.7/3.5.4. This issue affects some unknown functionality of the component Object Signing Token Generator. The manipulation with an unknown input leads to a entropy vulnerability. Using CWE to declare the problem leads to CWE-331. The product uses an algorithm or scheme that produces insufficient entropy, leaving patterns or clusters of values that are more likely to occur than others. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

ExpressionEngine version 2.x < 2.11.8 and version 3.x < 3.5.5 create an object signing token with weak entropy. Successfully guessing the token can lead to remote code execution.

The bug was discovered 04/10/2017. The weakness was published 06/22/2017 (Website). It is possible to read the advisory at docs.expressionengine.com. The identification of this vulnerability is CVE-2017-0897 since 11/30/2016. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1600.001 according to MITRE ATT&CK.

The vulnerability was handled as a non-public zero-day exploit for at least 73 days. During that time the estimated underground price was around $0-$5k.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at SecurityFocus (BID 99242†). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Name

• ExpressionEngine

Version

• 2.11.0
• 2.11.1
• 2.11.2
• 2.11.3
• 2.11.4
• 2.11.5
• 2.11.6
• 2.11.7
• 3.5.0
• 3.5.1
• 3.5.2
• 3.5.3
• 3.5.4

CPE 2.3info

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CPE 2.2info

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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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