Description (CNA)
Improper Encoding or Escaping of Output vulnerability in ninenines cowlib allows Link header directive smuggling via unescaped special characters in cow_link:link/1. cow_link:do_link/1 in cowlib interpolates the target URI, rel value, and attribute keys directly into the serialized Link: header value without escaping or token-grammar validation. A > byte in target prematurely closes the URI slot, allowing an attacker to append additional link entries with attacker-chosen rel directives. A " or \ in rel escapes the quoted string and opens new parameters. Any byte — including whitespace, =, and " — in an attribute key is emitted verbatim. Because browsers act on Link: directives such as rel="preconnect", rel="preload", and rel="prerender", an attacker who can influence these fields in an application that round-trips parsed Link headers through cow_link:link/1 can force victim browsers to make out-of-band connections to attacker-controlled origins. This issue affects cowlib: from 2.9.0 before 2.20.0.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| ninenines / cowlib | affected 2.9.0 before 2.20.0 |
| ninenines / cowlib | affected 485d58dfa91b91d98135dc95e5615f421715dae5 before 89da27ee4c241f5d649ba7d9b7f2188918af6cea |
CWE
CWE-116
References
- https://cna.erlef.org/cves/CVE-2026-43971.html
- https://osv.dev/vulnerability/EEF-CVE-2026-43971
- https://github.com/ninenines/cowlib/commit/485d58dfa91b91d98135dc95e5615f421715dae5
- https://github.com/ninenines/cowlib/commit/89da27ee4c241f5d649ba7d9b7f2188918af6cea
ADP enrichment
No English description supplied.
No references supplied.