CVE-2026-56813
Cookie attribute injection in Plug.Conn.Cookies.encode/2
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 1.19.0 before 1.19.5, from 1.20.0 before 1.20.3.
INFO
Published Date :
July 10, 2026, 1:16 p.m.
Last Modified :
July 10, 2026, 1:16 p.m.
Remotely Exploit :
No
Source :
6b3ad84c-e1a6-4bf7-a703-f496b71e49db
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | LOW | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | ||||
| CVSS 4.0 | LOW | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db |
Solution
- Update elixir-plug to version 1.16.6 or later.
- Update elixir-plug to version 1.17.4 or later.
- Update elixir-plug to version 1.18.5 or later.
- Update elixir-plug to version 1.19.5 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-56813.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-56813 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-56813
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-56813 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-56813 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Jul. 10, 2026
Action Type Old Value New Value Added Affected [{'cpes': ['cpe:2.3:a:elixir-plug:plug:*:*:*:*:*:*:*:*'], 'repo': 'https://github.com/elixir-plug/plug', 'vendor': 'elixir-plug', 'modules': ["'Elixir.Plug.Conn.Cookies'", "'Elixir.Plug.Conn'"], 'product': 'plug', 'versions': [{'status': 'affected', 'version': '0.1.0', 'lessThan': '1.16.6', 'versionType': 'semver'}, {'status': 'affected', 'version': '1.17.0', 'lessThan': '1.17.4', 'versionType': 'semver'}, {'status': 'affected', 'version': '1.18.0', 'lessThan': '1.18.5', 'versionType': 'semver'}, {'status': 'affected', 'version': '1.19.0', 'lessThan': '1.19.5', 'versionType': 'semver'}, {'status': 'affected', 'version': '1.20.0', 'lessThan': '1.20.3', 'versionType': 'semver'}], 'packageURL': 'pkg:hex/plug', 'packageName': 'plug', 'programFiles': ['lib/plug/conn/cookies.ex'], 'collectionURL': 'https://repo.hex.pm', 'defaultStatus': 'unaffected', 'programRoutines': [{'name': "'Elixir.Plug.Conn.Cookies':encode/2"}, {'name': "'Elixir.Plug.Conn':put_resp_cookie/4"}]}, {'cpes': ['cpe:2.3:a:elixir-plug:plug:*:*:*:*:*:*:*:*'], 'repo': 'https://github.com/elixir-plug/plug', 'vendor': 'elixir-plug', 'modules': ["'Elixir.Plug.Conn.Cookies'", "'Elixir.Plug.Conn'"], 'product': 'plug', 'versions': [{'status': 'affected', 'changes': [{'at': '3f00dfad4e20ba88472e315c90a25742bf178f8e', 'status': 'unaffected'}, {'at': 'a6d1248659022749869963fd302687165ecf8c8b', 'status': 'unaffected'}, {'at': '4167981747fe9ce75f374b94a28861ae950ea992', 'status': 'unaffected'}, {'at': '149d9ed68fee0b4f77efd1e835ce5d785856697b', 'status': 'unaffected'}, {'at': 'eceb8315ce9a31ef784943a95a8624ebd1bc7e06', 'status': 'unaffected'}], 'version': 'f26876aa67aaeb38e616638aa3efbcc2fe2906a5', 'lessThan': '*', 'versionType': 'git'}], 'packageURL': 'pkg:github/elixir-plug/plug', 'packageName': 'elixir-plug/plug', 'programFiles': ['lib/plug/conn/cookies.ex'], 'collectionURL': 'https://github.com', 'defaultStatus': 'unaffected', 'programRoutines': [{'name': "'Elixir.Plug.Conn.Cookies':encode/2"}, {'name': "'Elixir.Plug.Conn':put_resp_cookie/4"}]}] Added 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 1.19.0 before 1.19.5, from 1.20.0 before 1.20.3. Added CVSS V4.0 AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-141 Added Reference https://cna.erlef.org/cves/CVE-2026-56813.html Added Reference https://github.com/elixir-plug/plug/commit/c6575800b2c4e15af1904df87522ca8a23da020c Added Reference https://github.com/elixir-plug/plug/security/advisories/GHSA-wpmj-jh88-rpgm Added Reference https://osv.dev/vulnerability/EEF-CVE-2026-56813