| Name | CVE-2026-43971 |
| Description | 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 onward. |
| Source | CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
| Debian Bugs | 1145197 |
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| erlang-cowlib (PTS) | bookworm, trixie | 1.3.0-3 | fixed |
| forky, sid | 2.19.0-1 | vulnerable |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| erlang-cowlib | source | bullseye | (not affected) | |||
| erlang-cowlib | source | bookworm | (not affected) | |||
| erlang-cowlib | source | trixie | (not affected) | |||
| erlang-cowlib | source | (unstable) | (unfixed) | 1145197 |
[trixie] - erlang-cowlib <not-affected> (Vulnerable code not present)
[bookworm] - erlang-cowlib <not-affected> (Vulnerable code not present)
[bullseye] - erlang-cowlib <not-affected> (Vulnerable code not present)
https://cna.erlef.org/cves/CVE-2026-43971.html
https://osv.dev/vulnerability/EEF-CVE-2026-43971
Fixed by: https://github.com/ninenines/cowlib/commit/89da27ee4c241f5d649ba7d9b7f2188918af6cea