An API gateway often forwards the same request across several trust zones. CVE-2026-42037 matters when one of those forwarding steps uses an affected Axios version and carries attacker-controlled file metadata into multipart FormData. The bug can place extra lines in a multipart part header even though the outer HTTP request appears valid.
The advisory covers Axios versions from 1.0.0 through releases before 1.15.1. GitHub rates the issue CVSS 3.1 5.3 and CWE-93. The public request path has low complexity, but exploitation depends on a specific forwarding design and downstream parser behavior.
Where a gateway becomes exposed
A gateway that accepts multipart uploads may forward a file to a scanner, object store, processing service, or internal API. If it takes a client-supplied MIME type and creates a Blob or File-like object for Axios without validation, the Blob type can carry CRLF sequences.
The vulnerable serializer interpolates value.type into the multipart part Content-Type line. The string path in the same Axios helper had line-break neutralization, while the Blob path did not. Node.js blocks line breaks in outer HTTP headers, but the injected bytes are inside the multipart body generated by Axios.
The receiving parser may treat the added line as a separate part header. The advisory lists possible bypass of Content-Type filters, parser confusion, and phantom form fields if the boundary is known. Gateways commonly sit in front of services that make routing or filtering decisions, which is why the downstream consequence matters as much as the package version.
Review the forwarding chain
Start at the public route and follow the file object through each hop. Record the MIME value's source, the code that constructs FormData, the Axios version at that hop, and the parser on the receiving side. A gateway may call a shared upload client that masks the direct Axios use.
Compare services that overwrite the client type with those that preserve it. A constant internal type narrows the path, while passing a header through unchanged keeps attacker influence. Authentication does not automatically eliminate the issue if an authenticated user can submit a crafted file type.
The receiver should not treat a per-part header as authoritative when its own policy knows the allowed file set. Validate the full MIME field, the filename, and the content. A content-based check can provide a stronger classification than a client-supplied media type.
Patch and verify the gateway artifact
Upgrade Axios to 1.15.1 or later. The official release notes list CRLF stripping in multipart headers. Pull request #10758 strips CR and LF from Blob.type, defaults a missing type to application/octet-stream, preserves valid types, and percent-encodes filenames.
Rebuild the gateway image or deployment package and inspect the Axios version inside the running artifact. Verify the upstream gateway, sidecar, and internal relay separately if each has its own package tree. A patched edge service does not fix an unpatched internal forwarder.
Add a local test that forwards a Blob with CRLF in its type through the real gateway path. The receiver should not observe an injected header line. Test an allowed media type and a missing type as controls. Keep the test in the deployment pipeline so a dependency override or wrapper regression is visible.
Detection and incident boundaries
Useful signals include multipart parser errors, unexpected per-part headers, Content-Type values containing encoded line-break text, and a mismatch between the gateway's view of a file and the receiving service's classification. Logs should identify the route, service version, and policy decision without storing sensitive file contents.
A malformed request does not prove compromise. Correlate it with an affected version, attacker-controlled input, and a downstream consequence. The advisory has a public proof of concept; CISA enrichment records exploitation as poc and automatable as no. This review found no KEV entry or active exploitation report.
Exposure context
ZoomEye Search app="Node.js" returned 5,548,145 fingerprint matches. The exact CVE Filter returned 0. The Search describes broad Node.js exposure, not a list of vulnerable gateways or confirmed victims.
Remediation check
The gateway work is complete when every forwarding hop runs a fixed Axios version, upload metadata is validated at the boundary, the receiving parser has its own policy, and a negative integration test proves that CRLF cannot enter a part header. Those checks address both the library defect and the multi-hop trust problem around it.