CVE-2026-43966: HTTP Response Splitting via Non-VCHAR Bytes in cow_http_struct_hd:escape_string/2
ninenines · cowlib
Fixed in 2.22.0 · Affected: ninenines cowlib before 2.22.0 · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 17% of scored CVEs
DescriptionCVE.org
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 before 2.22.0.
Affected products2
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- ninenines · cowlibfrom 2.9.0 before 2.22.0
- ninenines · cowlibVersions not stated
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CoverageNo articles yet
No CyberSIXT article names CVE-2026-43966 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.