Is CVE-2026-5079 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-5079 being exploited in the wild.

How severe is CVE-2026-5079?

High severity, with a CVSS score of 7.5, published 15 June 2026.

Which products and versions are affected?

multer (npm) SEMVER:introduced=1.0.0,fixed=2.2.0; OpenJS Foundation Multer >= 1.0.0, = 3.0.0-alpha.1, < 3.0.0-alpha.2.

Is there a fix for CVE-2026-5079?

Yes. multer (npm): upgrade to 2.2.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-5079 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-5079?

Check whether you run multer (npm) or OpenJS Foundation Multer at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-5079: OpenJS Multer Denial of Service via deeply nested field names

Q: Is there a fix for CVE-2026-5079?

Yes. multer (npm): upgrade to 2.2.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: How is CVE-2026-5079 attacked?

It is attacked over the network, in a software library.

Q: Am I affected by CVE-2026-5079?

Check whether you run multer (npm) or OpenJS Foundation Multer at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-5079 · Severity: high · CVSS 7.5 · Published 2026-06-15

Multer, a popular middleware for handling file uploads in web applications, is vulnerable to a Denial of Service (DoS) attack. An attacker can send a specially crafted request with deeply nested field names to exhaust the server's CPU and memory resources. This can lead to application crashes or significant performance degradation, preventing legitimate users from accessing the service.

Technologies: multer (npm), OpenJS Foundation Multer. Vendors: npm, OpenJS Foundation.

Quick answers

Is CVE-2026-5079 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-5079 being exploited in the wild.
How severe is CVE-2026-5079?: High severity, with a CVSS score of 7.5, published 15 June 2026.
Which products and versions are affected?: multer (npm) SEMVER:introduced=1.0.0,fixed=2.2.0; OpenJS Foundation Multer >= 1.0.0, < 2.2.0; >= 3.0.0-alpha.1, < 3.0.0-alpha.2.
Is there a fix for CVE-2026-5079?: Yes. multer (npm): upgrade to 2.2.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-5079 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-5079?: Check whether you run multer (npm) or OpenJS Foundation Multer at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

multer (npm): upgrade to 2.2.0 or later
```
npm install multer@2.2.0
```

Technical details

Multer is vulnerable to Uncontrolled Resource Consumption (CWE-400) due to how its dependency, `append-field`, handles bracket notation in multipart form field names (e.g., `a[b][c]`). The parser does not enforce a limit on nesting depth, allowing a remote, unauthenticated attacker to submit a single HTTP request that forces the server to allocate deeply nested object structures. This process consumes excessive CPU and memory, leading to a Denial of Service. The issue is resolved in version 2.2.0, which introduces the `limits.fieldNestingDepth` configuration option.

Affected products

expressjs multer >= 1.0.0, < 2.2.0; >= 3.0.0-alpha.1, < 3.0.0-alpha.2

Identifiers

CVE-2026-5079
GHSA-72gw-mp4g-v24j

Timeline

2026-06-15: disclosed
2026-06-17: advisory
2026-06-17: patched: Fixed in version 2.2.0 and 3.0.0-alpha.2

References

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