How severe is CVE-2026-5038?

CVE-2026-5038 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 CVE-2026-5038?

CVE-2026-5038 affects the following packages: multer (npm), multer (npm). Ecosystems affected: npm.

How do I fix CVE-2026-5038?

Update multer to 2.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-5038 is resolved across your whole dependency graph.

How do I detect CVE-2026-5038 in my npm dependencies?

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

How do I mitigate CVE-2026-5038 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-5038 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-5038 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 CVE-2026-5038?

CVE-2026-5038 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 31th 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 CVE-2026-5038?

CVE-2026-5038 is classified as CWE-459 (CWE-459). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-5038 published, and has it been updated?

CVE-2026-5038 was published on June 15, 2026 and was last updated on October 28, 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

CVE-2026-5038 — multer

MEDIUM

CVE-2026-5038 is a medium-severity (CVSS 5.3) CWE-459 vulnerability in multer. A fix is available for multer — see the affected versions and patch details below.

multer vulnerable to Denial of Service via incomplete cleanup of aborted uploads

Also known asGHSA-3p4h-7m6x-2hcm

Published

Jun 15, 2026

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Nov 7, 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 CVE-2026-5038.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs31th percentile — riskier than 31% of all scored CVEsHighest risk

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

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs 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.

7Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

multernpm

31.0Mdownloads / week

Description

Impact: multer versions 2.0.0-alpha.1 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service when using diskStorage. Aborted or malformed multipart uploads leave orphaned partial files on disk because the Readable.pipe() call does not propagate the stream destroy signal to the underlying fs.WriteStream. An attacker can exhaust disk space by triggering many aborted uploads, with no application bug required.

Patches: Users should upgrade to multer 2.2.0 (2.x line) or 3.0.0-alpha.2 (3.x prerelease). Both versions track in-flight write streams and clean them up on the abort path.

Workarounds: None.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`multer`	≥ 2.0.0-alpha.1&&< 2.2.0	2.2.0`npm install multer@2.2.0`
📦npm	`multer`	≥ 3.0.0-alpha.1&&< 3.0.0-alpha.2	3.0.0-alpha.2`npm install multer@3.0.0-alpha.2`

Affected Products

1 product · 2 configurations

Application

multerexpressjs

≥ 2.0.0 && < 2.2.0

1 version

3.0.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for multer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update multer to 2.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-5038 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

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 HatImportant

This is an Important denial of service vulnerability in `multer` when configured to use `diskStorage`. An attacker can exploit this flaw by initiating and then aborting or sending malformed multipart uploads, leading to the accumulation of orphaned partial files and eventual disk space exhaustion on affected Red Hat…

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 CVE-2026-5038 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat Ansible Automation Platform 2.1	`ansible-automation-platform/automation-portal:1790254963`	RHSA-2026:72712
Red Hat Ansible Automation Platform 2.2	`ansible-automation-platform/bootc-automation-portal-rhel9:1790657374`	RHSA-2026:73404
Red Hat Developer Hub 1.10	`rhdh/red-hat-developer-hub-backstage-plugin-lightspeed-backend:1785332487`	RHSA-2026:48126
Red Hat Developer Hub 1.10	`rhdh/rhdh-hub-rhel9:1785411652`	RHSA-2026:49642
Red Hat Developer Hub 1.9	`rhdh/rhdh-hub-rhel9:1785972843`	RHSA-2026:52768