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Security Advisories: GSA_kwCzR0hTQS1xcmdmLTlncGMtdnJ4d84AAy5b
Bypass of CSRF protection in the presence of predictable userInfo
The CSRF protection enforced by the
@fastify/csrf-protection library in combination with
@fastify/cookie can be bypassed from network and same-site attackers under certain conditions.
@fastify/csrf-protection supports an optional
userInfo parameter that binds the CSRF token to the user. This parameter has been introduced to prevent cookie-tossing attacks as a fix for CVE-2021-29624. Whenever
userInfo parameter is missing, or its value can be predicted for the target user account, network and same-site attackers can 1. fixate a
_csrf cookie in the victim's browser, and 2. forge CSRF tokens that are valid for the victim's session. This allows attackers to bypass the CSRF protection mechanism.
As a fix,
@fastify/csrf-protection starting from version 6.3.0 (and v4.1.0) includes a server-defined secret
hmacKey that cryptographically binds the CSRF token to the value of the
_csrf cookie and the
userInfo parameter, making tokens non-spoofable by attackers. This protection is effective as long as the
userInfo parameter is unique for each user.
This is patched in version 6.3.0 and v4.1.0.
As a workaround, developers can use a random, non-predictable
userInfo parameter for each user.
- Pedro Adão (@pedromigueladao), Instituto Superior Técnico, University of Lisbon
- Marco Squarcina (@lavish), Security & Privacy Research Unit, TU Wien
Source: GitHub Advisory Database
Published: 5 months ago
Updated: 5 months ago
CVSS Score: 5.3
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
Identifiers: GHSA-qrgf-9gpc-vrxw, CVE-2023-27495
Fixed in: 6.3.0, 4.1.0