Security readout for executives and security teams
Plain-English summary
CVE-2026-3520 affects Multer, a common Node.js file-upload middleware. Vulnerable versions before 2.1.1 can be crashed by malformed upload requests, causing denial of service. This is most urgent for internet-facing applications that accept multipart/form-data uploads. Sources do not indicate confirmed active exploitation.
Executive priority
Prioritize remediation for public upload services and customer-facing APIs. The risk is service disruption, not data theft based on current sources, but exploitation requires no authentication and low complexity.
Technical view
Multer before 2.1.1 has uncontrolled recursion that can be triggered through malformed multipart requests, potentially causing stack overflow and availability loss. CVSS 4.0 is 8.7 with network attack vector, low complexity, no privileges, and no user interaction. Listed weaknesses include CWE-674 and CWE-770.
Likely exposure
Exposure is likely where Node.js or Express applications use Multer before 2.1.1 to process file uploads or other multipart/form-data requests, especially on public endpoints.
Exploitation context
An unauthenticated remote attacker may be able to send malformed multipart requests that crash or exhaust the application process. KEV is false, and the provided sources do not report active exploitation.
Researcher notes
The public record points to uncontrolled recursion and resource exhaustion in multipart parsing. The fixing commit is referenced publicly. Avoid assuming affected downstream products beyond environments that include vulnerable Multer versions or vendor advisories that explicitly mention impact.
Mitigation direction
- Upgrade Multer to version 2.1.1 or later.
- If using Red Hat-packaged software, review the listed RHSA advisories.
- Check vendor guidance for environment-specific remediation.
- No workaround is identified in the provided advisory sources.
Validation and detection
- Inventory package manifests and lockfiles for Multer versions below 2.1.1.
- Identify application routes that process multipart/form-data through Multer.
- Confirm deployed containers and builds include the upgraded dependency.
- Review availability monitoring for unexplained crashes on upload endpoints.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-674: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-770: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-3520 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.7 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N——openjsCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADPVulnerability scoring details
Base CVSS 4.0 score
8.7HighVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- ADP timelineredhat-SADP
Made public.
- CVE publishedCVE Program
The CVE record was published.
- ADP timelineredhat-SADP
Reported to Red Hat.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2026-03-04T17:01:43.432Z: Reported to Red Hat.
- 2026-03-04T16:17:18.962Z: Made public.
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/expressjs/multer/security/advisories/GHSA-5528-5vmv-3xc2CVE reference, openjs
- https://www.cve.org/CVERecord?id=CVE-2026-3520CVE reference, openjs
- https://github.com/expressjs/multer/commit/7e66481f8b2e6c54b982b34c152479e096ce2752CVE reference, openjs
- https://cna.openjsf.org/security-advisories.htmlCVE reference, openjs
- https://access.redhat.com/security/cve/CVE-2026-3520CVE reference, redhat-SADP · vdb-entry, x_refsource_REDHAT
- RHBZ#2444584CVE reference, redhat-SADP · issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-3520.jsonCVE reference, redhat-SADP · x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:6174CVE reference, redhat-SADP · vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:6802CVE reference, redhat-SADP · vendor-advisory, x_refsource_REDHAT
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Uncontrolled Recursion
Uncontrolled Recursion represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Allocation of Resources Without Limits or Throttling
Allocation of Resources Without Limits or Throttling represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.