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Vulnerability · Published Oct 26, 2026 · Assigned by EEF

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

Low 2.1

In plain English

A low-severity security flaw in hackney from benoitc. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 8% of all known vulnerabilities).

Severity (CVSS 4.0)2.1Low
Exploit odds (30 days)0.2%top 91.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

VendorProductVersions
benoitc hackney 2.0.0 – before 4.9.0
benoitc hackney 5df5a74a2817d5b12880d217db33253ff1fae1b5 – before 5ee7d7d19eba27e774667d472feb1e93a08af7f9

Weakness: CWE-113 · Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N

References