Vulnerability in multer (CVE-2026-5038)
Summary
Vulnerability in multer (CVE-2026-5038). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 3.0.0-alpha.2 or later.
Original description
The description as published by the source.
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.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-5038 has been found in multer.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade multer to 3.0.0-alpha.2 or later.
If unsure, ask your IT team or search "multer CVE-2026-5038" on the vendor's site.
CVE-2026-5038 (multer) — CWE-459 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 3.0.0-alpha.2 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-459) exists in multer.
Check the vendor advisory for the affected versions of multer.
Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.
Update to 3.0.0-alpha.2.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'multer' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'multer' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
multerを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade multer to 3.0.0-alpha.2ステージング環境で 3.0.0-alpha.2 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory cna.openjsf.org
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- web github.com