Struts2 S2-061 Remote Code Execution Vulnerability (CVE-2020-17530) Threat Alert

Struts2 S2-061 Remote Code Execution Vulnerability (CVE-2020-17530) Threat Alert

January 4, 2021 | Mina Hao

Overview

On December 8, 2020, Struts released a security bulletin disclosing a potential remote code execution vulnerability (CVE-2020-17530) in S2-061.

The vulnerability stems from insufficient input validation. This results in two forced Object Graph Navigation Library (OGNL) evaluations when the original user input is calculated.

When the OGNL expression is forced in Struts tag attributes and can be modified by external input, an attacker could craft a malicious OGNL expression to trigger the vulnerability.

The vulnerability has been fixed in Struts 2.5.26. Affected users are advised to upgrade to Struts 2.5.26 without delay.

For more information, see Struts’s security bulletin at the following link:

https://cwiki.apache.org/confluence/display/WW/S2-061

Affected Versions

  • Struts 2.0.0 – Struts 2.5.25

Unaffected Versions

  • Struts version >=  Struts 2.5.26

Solution

Struts has officially released a new version to fix the preceding vulnerability. Users are advised to upgrade as soon as possible.

If users cannot upgrade for the time being, they should avoid using forced OGNL evaluation on untrusted user input to reduce risks.

The official security bulletin is available at the following link:

https://struts.apache.org/security/#do-not-use-incoming-untrusted-user-input-in-forced-expression-evaluation

Statement

This advisory is only used to describe a potential risk. NSFOCUS does not provide any commitment or promise on this advisory. NSFOCUS and the author will not bear any liability for any direct and/or indirect consequences and losses caused by transmitting and/or using this advisory. NSFOCUS reserves all the rights to modify and interpret this advisory. Please include this statement paragraph when reproducing or transferring this advisory. Do not modify this advisory, add/delete any information to/from it, or use this advisory for commercial purposes without permission from NSFOCUS.

About NSFOCUS

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