Vulnerability in multer (CVE-2026-77063)
Summary
Vulnerability in multer (CVE-2026-77063). Risk of unauthorized operations or information disclosure. Exploitable via multer. Mitigation: upgrade to 2.3.0 or later.
Original description
The description as published by the source.
multer is a middleware for handling multipart/form-data in Node.js. When an application uses an asynchronous fileFilter together with the fileSize limit, a race condition in multer's file stream handling can allow a file that exceeds the configured size limit to bypass the size-limit rejection. All versions before 2.3.0 are affected. The impact is limited because the underlying multipart parser still truncates the stream at the size limit, so this is a bypass of the limit rejection rather than uncontrolled resource consumption. The issue is fixed in multer 2.3.0. Upgrade to multer 2.3.0 to remediate.
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-2026-77063 has been found in multer.
Attackers can target a specific entry point like multer over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 3.7/10.
What to do: upgrade multer to 2.3.0 or later.
If unsure, ask your IT team or search "multer CVE-2026-77063" on the vendor's site.
CVE-2026-77063 (multer) — CWE-362 / CVSS v3 3.7
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: multer / fileFilter / limits.fileSize / LIMIT_FILE_SIZE
Patched: 2.3.0 — apply immediately
Workaround: Use a synchronous fileFilter, or validate the uploaded file size after the upload completes.
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-362) exists in multer. Attackers reach the vulnerable code path via multer without authentication.
Check the vendor advisory for the affected versions of multer. Attack surface: multer / fileFilter / limits.fileSize / LIMIT_FILE_SIZE.
Severity: Low (CVSS 3.7/10). Risk of unauthorized operations or information disclosure.
Update to 2.3.0.
Workaround: Use a synchronous fileFilter, or validate the uploaded file size after the upload completes.
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 temporary workaround mitigate
Use a synchronous `fileFilter`, or validate the uploaded file size after the upload completes.パッチが適用されるまでの応急処置として、Use a synchronous
fileFilter, or validate the uploaded file size after the upload completes. を実施。回避策の副作用 (機能低下) を確認した上で。 -
3Apply patch patch
Upgrade multer to 2.3.0ステージング環境で 2.3.0 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。
-
4Post-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
- web github.com
- web github.com