CVE-2026-43966

Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values. cow_http_struct_hd:escape_string/2 in cowlib only escapes \ and ", passing all other bytes through verbatim. This creates an encoder/decoder asymmetry: the matching parser accepts only printable ASCII (0x20–0x7E, excluding " and \), but the encoder emits any byte including CR and LF. An application that builds a structured HTTP header via cow_http_struct_hd:item/1 (or a higher-level wrapper such as cow_http_hd:wt_protocol/1) from attacker-controlled input can have \r\n injected into the serialized header value. Once on the wire, the injected CRLF terminates the current header and any following bytes are interpreted as a new header, enabling HTTP response splitting. This issue affects cowlib from 2.9.0.

CVSS

No CVSS.

References

Link	Resource
https://cna.erlef.org/cves/CVE-2026-43966.html
https://github.com/ninenines/cowboy/commit/f77cb9b5e730e300fffb551db1ba5d1c4ed878ef
https://github.com/ninenines/gun/commit/4f35609eb37109b106a863fc9ba83d7ee64e3e42
https://osv.dev/vulnerability/EEF-CVE-2026-43966

Configurations

No configuration.

History

08 Jun 2026, 17:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-06-08 17:16

Updated : 2026-06-09 15:20

NVD link : CVE-2026-43966

Mitre link : CVE-2026-43966

CVE.ORG link : CVE-2026-43966

JSON object : View

Products Affected

No product.

CWE

CWE-113

Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')

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