CVE-2026-76949

ash_authentication · Vulnerability

CVSS 4.0 9.1 CRITICALCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-76949

Published

Authentication Bypass by Spoofing vulnerability in team-alembic ash_authentication allows an attacker who can plant a remember-me cookie in a victim's browser to replace that victim's authenticated session with one for the attacker's own account. AshAuthentication.Plug.Helpers.sign_in_using_remember_me/3 skips re-authenticating an already-signed-in visitor by checking the session for "<subject_name>_token", but store_in_session/2 writes that key only when require_token_presence_for_authentication? is enabled and otherwise writes the bare subject name. At the default setting the guard therefore reads a key that is never written, its already-signed-in branch is unreachable, and the remember-me sign-in runs on every request through the per-request browser pipeline plug. A planted remember-me cookie is consequently honoured even for a visitor holding a live authenticated session, so whatever the victim enters afterwards lands in data the attacker controls. The read path in authenticate_resource_from_session/4 selects the key correctly, so the guard and the reader disagree about which key holds the session. This issue affects ash_authentication: from 4.10.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-76949

Published

ash_authentication

https://repo.hex.pm

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "collectionURL": "https://repo.hex.pm",
                    "cpes": [
                        "cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"
                    ],
                    "defaultStatus": "unaffected",
                    "modules": [
                        "'Elixir.AshAuthentication.Plug.Helpers'"
                    ],
                    "packageName": "ash_authentication",
                    "packageURL": "pkg:hex/ash_authentication",
                    "product": "ash_authentication",
                    "programFiles": [
                        "lib/ash_authentication/plug/helpers.ex"
                    ],
                    "programRoutines": [
                        {
                            "name": "'Elixir.AshAuthentication.Plug.Helpers':sign_in_using_remember_me/3"
                        },
                        {
                            "name": "'Elixir.AshAuthentication.Plug.Helpers':store_in_session/2"
                        }
                    ],
                    "repo": "https://github.com/team-alembic/ash_authentication",
                    "vendor": "team-alembic",
                    "versions": [
                        {
                            "lessThan": "4.15.0",
                            "status": "affected",
                            "version": "4.10.0",
                            "versionType": "semver"
                        },
                        {
                            "lessThan": "5.0.0-rc.14",
                            "status": "affected",
                            "version": "5.0.0-rc.0",
                            "versionType": "semver"
                        }
                    ]
                }

team-alembic/ash_authentication

https://github.com

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "collectionURL": "https://github.com",
                    "cpes": [
                        "cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"
                    ],
                    "defaultStatus": "unaffected",
                    "modules": [
                        "'Elixir.AshAuthentication.Plug.Helpers'"
                    ],
                    "packageName": "team-alembic/ash_authentication",
                    "packageURL": "pkg:github/team-alembic/ash_authentication",
                    "product": "ash_authentication",
                    "programFiles": [
                        "lib/ash_authentication/plug/helpers.ex"
                    ],
                    "programRoutines": [
                        {
                            "name": "'Elixir.AshAuthentication.Plug.Helpers':sign_in_using_remember_me/3"
                        },
                        {
                            "name": "'Elixir.AshAuthentication.Plug.Helpers':store_in_session/2"
                        }
                    ],
                    "repo": "https://github.com/team-alembic/ash_authentication",
                    "vendor": "team-alembic",
                    "versions": [
                        {
                            "changes": [
                                {
                                    "at": "b9568a53b438247238b1c5a4f49c8d84650f4bba",
                                    "status": "unaffected"
                                },
                                {
                                    "at": "9a34136b844abe179da1075067cf2835c64dcc12",
                                    "status": "unaffected"
                                }
                            ],
                            "lessThan": "*",
                            "status": "affected",
                            "version": "3d3de314692558d06ec13945f857f00514e95a8c",
                            "versionType": "git"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON