Bug 2515527 (CVE-2026-73649)

Summary: CVE-2026-73649 velocityjs: Velocity.js: Remote Code Execution via property-read to Function constructor (bypass of CVE-2026-44966 fix)
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: gmalinko, janstey, pdelbell, rstepani
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Velocity.js, a JavaScript implementation of the Apache Velocity template engine. An incomplete fix for a previous vulnerability allowed an attacker to bypass security filters by using unfiltered property-read expressions in templates. This enables an attacker-controlled template to access the JavaScript Function constructor, leading to arbitrary code execution. Successful exploitation could allow an attacker to execute arbitrary shell commands, access environment variables, cloud credentials, and internal network resources on the server.
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Description OSIDB Bzimport 2026-08-13 18:27:07 UTC 
Velocity.js is a JavaScript implementation of the Apache Velocity template engine. Prior to 2.1.7, the earlier fix for CVE-2026-44966 filtered constructor, __proto__, and prototype only in the #set assignment handler in src/compile/set.ts, while property-read expressions in src/compile/references.ts remained unfiltered. The getReferences() flow called getAttributes(), whose property access allowed an attacker-controlled template to traverse constructor.constructor to the JavaScript Function constructor. The #set handler validated only the assignment target and did not inspect the right-hand property-read expression, allowing arbitrary shell commands, environment-variable access, cloud-credential access, and internal-network access in the server process. This issue is fixed in version 2.1.7.