CVE-2021-43837
Jinja2 is a powerful templating engine and is not designed to safely render arbitrary templates.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (5.00%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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.
- CVSS 3.1
- 9.1 CRITICALCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
- EPSS
- 5.00% probability · 92th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-74, CWE-94
- Affected
- vault-cli project/vault-cli
- Source
- security-advisories@github.com
References
- https://github.com/peopledoc/vault-cli/commit/3ba3955887fd6b7d4d646c8b260f21cebf5db852Patch, Third Party Advisory
- https://github.com/peopledoc/vault-cli/security/advisories/GHSA-q34h-97wf-8r8jExploit, Mitigation, Third Party Advisory
- https://podalirius.net/en/publications/grehack-2021-optimizing-ssti-payloads-for-jinja2/Exploit, Third Party Advisory
- https://github.com/peopledoc/vault-cli/commit/3ba3955887fd6b7d4d646c8b260f21cebf5db852Patch, Third Party Advisory
- https://github.com/peopledoc/vault-cli/security/advisories/GHSA-q34h-97wf-8r8jExploit, Mitigation, Third Party Advisory
- https://podalirius.net/en/publications/grehack-2021-optimizing-ssti-payloads-for-jinja2/Exploit, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.