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CVE-2026-87859

MEDIUMCVSS 5.3/10EPSS 0.39%

Last modified

CVE-2026-87859 is a medium-severity vulnerability rated 5.3/10 on the CVSS scale. 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. EPSS estimates a 0.39% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1
5.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS Probability
0.39%

33.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
morganmorgan< 1.12.1

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-87859?
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.
How severe is CVE-2026-87859?
CVE-2026-87859 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 0.39% probability of exploitation in the next 30 days.
How do I fix CVE-2026-87859?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST