CVE-2026-5079: Impact: multer versions 1.0.0 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service via deeply

Q: How do I fix CVE-2026-5079?

multer: upgrade to 2.2.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-5079 being exploited?

CVE-2026-5079 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-5079 affect?

CVE-2026-5079 affects multer. Severity is high (CVSS 7.5). Impact: multer versions 1.0.0 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service via deeply nested field names in multipart form data. The append-field dependency parses bracket notation in field names with no limit on ne

Q: How urgent is CVE-2026-5079?

Priority 36/100. High severity; Remotely exploitable, no login, no user action

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-5079 is a high-severity flaw (CVSS 7.5) affecting multer. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Impact: multer versions 1.0.0 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service via deeply nested field names in multipart form data. The append-field dependency parses bracket notation in field names with no limit on nesting depth, allowing an attacker to force allocation of deeply nested object structures that consume CPU and memory. A single HTTP request with a crafted multipart body is sufficient to exploit this. Patches:

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 80%)
CISA exploited list	No
Weakness	CWE-400
Published	2026-06-15
Last modified	2026-06-17

Publisher (CNA): openjs · Vendor: expressjs

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-15 14:16 UTCPublished CVE record published
2026-06-17 10:58 UTCUpdated Record last modified

expressjs multer UPGRADE

Affected: >= 1.0.0 and < 2.2.0 · 3.0.0 alpha1

Fixed in: 2.2.0

Safe to downgrade to: a release before 1.0.0

1. Check installed version

npm ls multer

2. UPGRADE to 2.2.0

npm install multer@">=2.2.0"

3. If no update is available yet, DOWNGRADE to a release before 1.0.0

npm view multer versions npm install multer@"<1.0.0"

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-5079?

multer: upgrade to 2.2.0. Exact commands for each OS are on this page.

Is CVE-2026-5079 being exploited?

CVE-2026-5079 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-5079 affect?

CVE-2026-5079 affects multer. Severity is high (CVSS 7.5). Impact: multer versions 1.0.0 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service via deeply nested field names in multipart form data. The append-field dependency parses bracket notation in field names with no limit on ne

How urgent is CVE-2026-5079?

Priority 36/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-5038 MEDIUM 5.3 UPGRADE 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 wh

References

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