Answer in brief
CVE-2026-43966 records a Medium severity security vulnerability in cowboy and gun affected by an HTTP Request/Response Splitting vulnerability. The source record does not mark it as known exploited. 2 affected packages are mapped in the feed.
Answer in brief
CVE-2026-43966 records a Medium severity security vulnerability in cowboy and gun affected by an HTTP Request/Response Splitting vulnerability. The source record does not mark it as known exploited. 2 affected packages are mapped in the feed.
Update cowboy to 2.16.0; gun to 2.16.0 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanVulnerability describes the vulnerability class recorded for this advisory. The current record does not mark CVE-2026-43966 as known exploited; continue to monitor the source for status changes. The feed includes package mappings that can be checked against lockfiles and deployed manifests.
| Package | Affected range | Fixed version |
|---|---|---|
| cowboyerlang | <2.16.0 | 2.16.0 |
| gunerlang | <2.4.0 | 2.16.0 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
CVE-2026-43966 records a Medium severity security vulnerability in cowboy and gun affected by an HTTP Request/Response Splitting vulnerability. The source record does not mark it as known exploited. 2 affected packages are mapped in the feed.
The source record does not mark it as known exploited.
Check lockfiles and deployed manifests for cowboy, gun.
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL GuardUpdate cowboy to 2.16.0; gun to 2.16.0 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanVulnerability describes the vulnerability class recorded for this advisory. The current record does not mark CVE-2026-43966 as known exploited; continue to monitor the source for status changes. The feed includes package mappings that can be checked against lockfiles and deployed manifests.
| Package | Affected range | Fixed version |
|---|---|---|
| cowboyerlang | <2.16.0 | 2.16.0 |
| gunerlang | <2.4.0 | 2.16.0 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
CVE-2026-43966 records a Medium severity security vulnerability in cowboy and gun affected by an HTTP Request/Response Splitting vulnerability. The source record does not mark it as known exploited. 2 affected packages are mapped in the feed.
The source record does not mark it as known exploited.
Check lockfiles and deployed manifests for cowboy, gun.
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL GuardImproper 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.
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.