A cross-site request forgery flaw was found in etcd 3.3.1 and earlier. An attacker can set up a website that tries to send a POST request to the etcd server and modify a key. Adding a key is done with PUT so it is theoretically safe (cant PUT from an HTML form or such) but POST allows creating in-order keys that an attacker can send.
Weakness
The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request.
Affected Software
| Name |
Vendor |
Start Version |
End Version |
| Etcd |
Redhat |
* |
3.3.1 (including) |
| Etcd |
Ubuntu |
artful |
* |
| Etcd |
Ubuntu |
bionic |
* |
| Etcd |
Ubuntu |
cosmic |
* |
| Etcd |
Ubuntu |
devel |
* |
| Etcd |
Ubuntu |
disco |
* |
| Etcd |
Ubuntu |
eoan |
* |
| Etcd |
Ubuntu |
esm-apps/bionic |
* |
| Etcd |
Ubuntu |
esm-apps/focal |
* |
| Etcd |
Ubuntu |
esm-apps/jammy |
* |
| Etcd |
Ubuntu |
esm-apps/noble |
* |
| Etcd |
Ubuntu |
esm-apps/xenial |
* |
| Etcd |
Ubuntu |
focal |
* |
| Etcd |
Ubuntu |
groovy |
* |
| Etcd |
Ubuntu |
hirsute |
* |
| Etcd |
Ubuntu |
impish |
* |
| Etcd |
Ubuntu |
jammy |
* |
| Etcd |
Ubuntu |
kinetic |
* |
| Etcd |
Ubuntu |
lunar |
* |
| Etcd |
Ubuntu |
mantic |
* |
| Etcd |
Ubuntu |
noble |
* |
| Etcd |
Ubuntu |
oracular |
* |
| Etcd |
Ubuntu |
upstream |
* |
| Etcd |
Ubuntu |
xenial |
* |
Potential Mitigations
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
- For example, use anti-CSRF packages such as the OWASP CSRFGuard. [REF-330]
- Another example is the ESAPI Session Management control, which includes a component for CSRF. [REF-45]
- Use the “double-submitted cookie” method as described by Felten and Zeller:
- When a user visits a site, the site should generate a pseudorandom value and set it as a cookie on the user’s machine. The site should require every form submission to include this value as a form value and also as a cookie value. When a POST request is sent to the site, the request should only be considered valid if the form value and the cookie value are the same.
- Because of the same-origin policy, an attacker cannot read or modify the value stored in the cookie. To successfully submit a form on behalf of the user, the attacker would have to correctly guess the pseudorandom value. If the pseudorandom value is cryptographically strong, this will be prohibitively difficult.
- This technique requires Javascript, so it may not work for browsers that have Javascript disabled. [REF-331]
References