CyberSecBulletin
CVE-2020-17530Exploited in the wildNVD status: Analyzed

Apache Struts Remote Code Execution

Published Updated By the CyberSecBulletin desk

CVE-2020-17530 is a critical-severity improper neutralization of special elements used in an expression language statement vulnerability in Apache Struts from Apache, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Apache Struts versions: Struts 2.0.0 - Struts 2.5.25. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on November 3, 2021, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Struts to 2.5.30 or a later version.
  2. CISA's required action: Apply updates per vendor instructions.
  3. Read the advisory on cwiki.apache.org for workarounds and exact fixed builds.
  4. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
ApacheApache StrutsStruts 2.0.0 - Struts 2.5.25Not stated
ApacheStruts2.0.0 up to, but not including, 2.5.302.5.30
OracleBusiness Intelligence12.2.1.3.0; 12.2.1.4.0Not stated
OracleCommunications Diameter Intelligence Hub8.0.0; 8.1.0; 8.2.0; 8.2.3Not stated
OracleCommunications Policy Management12.5.0Not stated
OracleCommunications Pricing Design Center12.0.0.3.0Not stated
OracleFinancial Services Data Integration Hub8.0.3; 8.0.6Not stated
OracleHospitality Opera 55.6Not stated
OracleMySQL Enterprise Monitor8.0.23Not stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.19.8CriticalNVD
CVSS 3.19.8CriticalCISA (ADP)
CVSS 2.07.5HighNVD

Official description

Forced OGNL evaluation, when evaluated on raw user input in tag attributes, may lead to remote code execution. Affected software : Apache Struts 2.0.0 - Struts 2.5.25.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Neutralization of Special Elements used in an Expression Language Statement

The product constructs all or part of an expression language (EL) statement in a framework such as a Java Server Page (JSP) using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended EL statement before it is executed.

How developers prevent this class of flaw

  • Avoid adding user-controlled data into an expression interpreter when possible.
  • If user-controlled data must be added to an expression interpreter, one or more of the following should be performed: Validate that the user input will not evaluate as an expression Encode the user input in a way that ensures it is not evaluated as an expression
  • The framework or tooling might allow the developer to disable or deactivate the processing of EL expressions, such as setting the isELIgnored attribute for a JSP page to true.

More Improper Neutralization of Special Elements used in an Expression Language Statement vulnerabilities (CWE-917)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. Deadline for US federal agencies to remediate, set by CISA.
  4. CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
  5. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in Apache Struts

All Apache Struts vulnerabilities

Recent Improper Neutralization of Special Elements used in an Expression Language Statement vulnerabilities

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