CVE Vulnerabilities

CVE-2021-43837

Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

Published: Dec 16, 2021 | Modified: Nov 21, 2024
CVSS 3.x
9.1
CRITICAL
Source:
NVD
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
CVSS 2.x
9 HIGH
AV:N/AC:L/Au:S/C:C/I:C/A:C
RedHat/V2
RedHat/V3
Ubuntu

vault-cli is a configurable command-line interface tool (and python library) to interact with Hashicorp Vault. In versions before 3.0.0 vault-cli features the ability for rendering templated values. When a secret starts with the prefix !template!, vault-cli interprets the rest of the contents of the secret as a Jinja2 template. Jinja2 is a powerful templating engine and is not designed to safely render arbitrary templates. An attacker controlling a jinja2 template rendered on a machine can trigger arbitrary code, making this a Remote Code Execution (RCE) risk. If the content of the vault can be completely trusted, then this is not a problem. Otherwise, if your threat model includes cases where an attacker can manipulate a secret value read from the vault using vault-cli, then this vulnerability may impact you. In 3.0.0, the code related to interpreting vault templated secrets has been removed entirely. Users are advised to upgrade as soon as possible. For users unable to upgrade a workaround does exist. Using the environment variable VAULT_CLI_RENDER=false or the flag --no-render (placed between vault-cli and the subcommand, e.g. vault-cli --no-render get-all) or adding render: false to the vault-cli configuration yaml file disables rendering and removes the vulnerability. Using the python library, you can use: vault_cli.get_client(render=False) when creating your client to get a client that will not render templated secrets and thus operates securely.

Weakness

The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.

Affected Software

Name Vendor Start Version End Version
Vault-cli Vault-cli_project 0.7.0 (including) 3.0.0 (excluding)

Potential Mitigations

References