Log in Start free

Vulnerability · Published Jul 10, 2026 · Assigned by EEF

CVE-2026-56813Cookie attribute injection in Plug.Conn.Cookies.encode/2

Low 2.1

In plain English

A low-severity security flaw in plug from elixir-plug. 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 12% of all known vulnerabilities).

Severity (CVSS 4.0)2.1Low
Exploit odds (30 days)0.2%top 88.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

Improper Neutralization of Parameter/Argument Delimiters vulnerability in elixir-plug plug allows an attacker to inject or override HTTP cookie attributes. The Plug.Conn.Cookies.encode/2 function in lib/plug/conn/cookies.ex builds the Set-Cookie response header by interpolating the cookie value and its path, domain, same_site, and extra attributes directly into the header without neutralizing the ; delimiter that separates cookie attributes. An application that places attacker-controlled data into a cookie value or attribute (for example via Plug.Conn.put_resp_cookie/4 when reflecting a username or preference) lets an attacker inject a ; to append or override cookie attributes (such as Domain and Path scope, or dropping the Secure and HttpOnly flags), enabling cookie tossing and session fixation. Carriage return, line feed, and null bytes are rejected by Plug.Conn header validation, so HTTP response splitting is not possible, but attribute injection through ; is not prevented. This issue affects plug: from 0.1.0 before 1.16.6, from 1.17.0 before 1.17.4, from 1.18.0 before 1.18.5, from 1.19.1 before 1.19.5, and from 1.20.0 before 1.20.3.

Affected products (as reported)

VendorProductVersions
elixir-plug plug 0.1.0 – before 1.16.61.17.0 – before 1.17.41.18.0 – before 1.18.51.19.1 – before 1.19.51.20.0 – before 1.20.3
elixir-plug plug f26876aa67aaeb38e616638aa3efbcc2fe2906a5 – before *

Weakness: CWE-141 · 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