CVE-2026-77063multer vulnerable to file size limit bypass via async fileFilter race condition
Updated under an hour ago ()
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It affects multer and 1 other product. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 3.7 LOW (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
- Weakness (CWE)
- CWE-362
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- openjs
- NVD analysis
- Analyzed
- Record last updated
- Aug 31, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
multer multer multer:multer (from the name) | before 2.3.0; 2.3.0 not affected | CNA record |
expressjs multer expressjs:multer | before 2.3.0 | NVD |
References
- https://github.com/expressjs/multer/security/advisories/GHSA-qvfw-j98x-7q72vendor-advisory, mitigation
- https://cna.openjsf.org/security-advisories.htmlvendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.