Bug 2531809 (CVE-2026-87859)

Summary: CVE-2026-87859 morgan: morgan: Log Injection via unescaped double quote in log fields
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: aazores, cmah, eaguilar, ebaron, gmalinko, janstey, jmatsuok, jtolenti, pdelbell, pjindal, rhel-process-autobot, rstepani, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in morgan, an HTTP request logger middleware for Node.js. An unauthenticated remote attacker can exploit this vulnerability by injecting an unescaped double quote into a log field they control, such as the User-Agent or Referer header. This causes the log field to close prematurely, leading a log parsing system to misinterpret subsequent attacker-controlled text as a different log field. This could result in the forging of log entries, potentially impacting the integrity of log data.
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Bug Depends On: 2535014    
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Description OSIDB Bzimport 2026-09-11 09:38:14 UTC 
morgan is an HTTP request logger middleware for Node.js. In versions before 1.12.1, its escapeLogField() function does not escape the double quote character, which delimits the quoted fields of the Apache combined log format that morgan emits. An unauthenticated remote attacker who controls a value written to a quoted field, such as the User-Agent or Referer header, can include a double quote to close that field early, so a log consumer that parses the log by field position reads attacker-supplied text as the following field. In the built-in formats this makes the recorded value differ from the value that was sent, and in custom formats that quote an attacker-controlled token before a server-controlled one it can forge values such as the response status. No newline is injected, so record separation stays intact. The issue is fixed in morgan 1.12.1, which escapes the double quote. Users should upgrade to morgan 1.12.1 or later.