# CVE-2026-5027: Langflow - Path Traversal Arbitrary File Write via upload_user_file

- Exploited (CISA KEV): no
- Published: 2026-03-27
- CVSS: 8.8 HIGH (v3.1)
- EPSS: 40.0% (99th percentile)
- CWE: CWE-22

The 'POST /api/v2/files' endpoint does not sanitize the 'filename' parameter from the multipart form data, allowing an attacker to write files to arbitrary locations on the filesystem using path traversal sequences ('../').

## Edge WAF coverage (claimed by vendors, not measured)

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | No public claim | — | — |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | No public claim | — | — |
| Fastly | Before feed history | — | — |
| F5 | Rule published | 2026-09-16 | 173 |
| Akamai | No public source | — | — |
| OWASP CRS | No public claim | — | — |

### F5

- 2026-09-16 · new · rule 200007111
  > Added: signature 200007111 "Langflow Arbitrary File Write" (Path Traversal, risk High), systems: Other Web Server. References: CVE-2026-5027.
  Source: https://docs.cloud.f5.com/docs-v2/platform/changelogs/security-details-changelog

## Our test (measured)

- OWASP Core Rule Set 4.25.0, paranoia level 1, anomaly threshold 5, default CRS settings: partial (2 of 4 requests blocked), template CVE-2026-5027, 2026-11-02
- OWASP Core Rule Set 4.25.0, paranoia level 2, anomaly threshold 5, default CRS settings: partial (2 of 4 requests blocked), template CVE-2026-5027, 2026-11-02

"No public claim" means no vendor statement names this CVE; "Before feed history" means the CVE is older than the vendor feed. In both cases generic rules may still block it.

HTML: https://cve.vigilbase.com/cve/CVE-2026-5027 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2026-5027