How severe is GHSA-jxfw-x594-9x9m?

GHSA-jxfw-x594-9x9m has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-jxfw-x594-9x9m?

GHSA-jxfw-x594-9x9m affects the following packages: morgan (npm). Ecosystems affected: npm.

How do I fix GHSA-jxfw-x594-9x9m?

Update morgan to 1.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-jxfw-x594-9x9m is resolved across your whole dependency graph.

How do I detect GHSA-jxfw-x594-9x9m in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for morgan, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-jxfw-x594-9x9m if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is GHSA-jxfw-x594-9x9m actively exploited in the wild?

No public exploit code has been indexed for GHSA-jxfw-x594-9x9m yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-jxfw-x594-9x9m?

GHSA-jxfw-x594-9x9m has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 21th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-jxfw-x594-9x9m?

GHSA-jxfw-x594-9x9m is classified as CWE-117 (CWE-117). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-jxfw-x594-9x9m published, and has it been updated?

GHSA-jxfw-x594-9x9m was published on September 8, 2026 and was last updated on September 8, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

MEDIUM severity

morgan vulnerable to Log Forging via unescaped Unicode line separatorsGHSA-jxfw-x594-9x9m

MEDIUMFix: expressjs/morgan@fbf9383

GHSA-jxfw-x594-9x9m is a medium-severity (CVSS 5.3) CWE-117 vulnerability in morgan. A fix is available for morgan — see the affected versions and patch details below.

Also known asCVE-2026-15603

Published

Sep 8, 2026

Updated

Sep 8, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-jxfw-x594-9x9m.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs21th percentile — riskier than 21% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-jxfw-x594-9x9m by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

10Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

morgannpm

8.4Mdownloads / week

Description

Impact

Morgan writes attacker-controlled request data to the access log through its tokens. The 1.11.0 fix neutralizes C0 control characters, DEL, and backslash, but it does not escape the Unicode line separators U+0085 (NEL), U+2028 (LINE SEPARATOR), or U+2029 (PARAGRAPH SEPARATOR). These code points are reachable through several tokens, including the request URL (:url), request headers such as :user-agent and :referrer, arbitrary :req[header] values, and the Basic auth username (:remote-user). NEL is valid obs-text in HTTP header values, so an attacker can place it in an ordinary request header.

When such a value is logged, the raw code points survive into the emitted access-log record, and downstream ECMAScript-aware or Unicode-aware log processing splits the single physical record into multiple logical records. This allows an attacker to forge log entries. The built-in combined, common, default, and short formats are affected, as well as any custom format. This is an incomplete fix of CVE-2026-5078.

Patches

Users should upgrade to version 1.12.0.

Workarounds

None. The affected values include the request URL and request headers, which are core to access logging, so there is no practical format-based mitigation. Upgrade to 1.12.0.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`morgan`	all versions	1.12.0`npm install morgan@1.12.0`

Affected Products

1 product · 1 configurations

Application

morganmorgan_project

< 1.12.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for morgan, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update morgan to 1.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-jxfw-x594-9x9m is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Log forging flaw in `morgan` allows unauthenticated remote attackers to inject Unicode line separators into log tokens. This can lead to log record misinterpretation by downstream systems, potentially impacting security monitoring and incident response in Red Hat products that use `morgan` as an HTTP request logger…

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

Source: Red Hat security advisory for GHSA-jxfw-x594-9x9m (CC BY 4.0)

Frequently Asked Questions

### Impact Morgan writes attacker-controlled request data to the access log through its tokens. The 1.11.0 fix neutralizes C0 control characters, DEL, and backslash, but it does not escape the Unicode line separators `U+0085` (NEL), `U+2028` (LINE SEPARATOR), or `U+2029` (PARAGRAPH SEPARATOR). These code points are reachable through several tokens, including the request URL (`:url`), request headers such as `:user-agent` and `:referrer`, arbitrary `:req[header]` values, and the Basic auth username (`:remote-user`). NEL is valid `obs-text` in HTTP header values, so an attacker can place it in