CVE-2026-112880: CRLF injection in Proxy-Authorization header built from proxy_auth_fun in hackney

Vulnerability summary

CVE-2026-112880 is a low (CVSS 2.1) vulnerability in benoitc hackney. EPSS estimates a 0.19% chance of exploitation in the next 30 days, higher than 8.5% of scored vulnerabilities.

Timeline

1. 26-10-2026
   PublishedVulnerability first disclosed.
2. 26-10-2026
   Last modifiedVulnerability information updated.

Description

Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in hackney_http_connect in benoitc hackney allows HTTP Request Splitting via the value a proxy_auth_fun callback returns. After a 407 response from an HTTP CONNECT proxy, hackney_http_connect:handle_proxy_auth/11 calls the caller's proxy_auth_fun with the status code and the response headers and writes the returned binary into the Proxy-Authorization line of the CONNECT retry without checking it. A CR, LF or NUL byte in that value adds header lines to the request sent to the proxy. The value is attacker-influenced when the callback derives it from untrusted data, for example from the proxy's challenge headers. Other caller-supplied values on the CONNECT path, such as the target host and the request headers, were already checked for control bytes. This issue affects hackney: from 2.0.0 before 4.9.0.

• CWE-113Improper Neutralization of CRLF Sequences in HTTP HeadersThe product receives data from an HTTP agent/component (e.g., web server, proxy, browser, etc.), but it does not neutralize or incorrectly neutralizes CR and LF characters before the data is included in outgoing HTTP headers.