elixir-plug plug/plug_crypto Plug.Crypto.verify/Plug.Crypto.secure_compare information disclosure

Summaryinfo

A vulnerability marked as problematic has been reported in elixir-plug plug and plug_crypto. Impacted is the function Plug.Crypto.verify/Plug.Crypto.secure_compare of the component plug_crypto. The manipulation leads to information disclosure. This vulnerability is traded as CVE-2026-105963. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in elixir-plug plug and plug_crypto (the affected version is unknown). This issue affects the function Plug.Crypto.verify/Plug.Crypto.secure_compare of the component plug_crypto. The manipulation with an unknown input leads to a information disclosure vulnerability. Using CWE to declare the problem leads to CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. Impacted is confidentiality. The summary by CVE is:

Externally-Generated Error Message Containing Sensitive Information vulnerability in plug_crypto in elixir-plug plug_crypto allows an unauthenticated remote attacker to expose the secret key base through application logs via a wrong-typed argument. Every public function in Plug.Crypto validates argument types in a function-head guard. A failed guard makes the Erlang VM raise FunctionClauseError with the actual argument values in the top stack frame, so the secret key base, a derived key, or the value an API key is compared against lands in that frame. The library's rescue blocks and Plug.Crypto.prune_args_from_stacktrace/1 only reach exceptions raised inside a function body, so they never see a guard failure. Plug.Cowboy and Bandit write the frame to the error log and attach it as crash_reason Logger metadata, which error trackers forward. Two entry points take request data. Plug.Crypto.verify/4 exposes the secret key base when the token is neither a binary nor nil, which Phoenix.Token.verify/4 reaches because it forwards the token unguarded. Plug.Crypto.secure_compare/2 exposes the other operand when one side is not a binary, as happens when a missing request header yields nil. Reading the leaked value needs separate access to the logs or the error tracker, so the request alone does not disclose the secret to the attacker. This issue affects plug: from 1.6.3 before 1.7.0; plug_crypto: from 1.0.0 before 2.2.1.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-105963 since 10/06/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/23/2026). The attack technique deployed by this issue is T1592 according to MITRE ATT&CK.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-108666). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

• elixir-plug

Name

• plug
• plug_crypto

Website

• Product: https://github.com/elixir-plug/plug/

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Be aware that VulDB is the high quality source for vulnerability data.

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