Non-constant-time SCIM token comparison in Zulip Server

Vulnerability Description

Zulip is an open-source team collaboration tool. For organizations with System for Cross-domain Identity Management(SCIM) account management enabled, Zulip Server 5.0 through 5.6 checked the SCIM bearer token using a comparator that did not run in constant time. Therefore, it might theoretically be possible for an attacker to infer the value of the token by performing a sophisticated timing analysis on a large number of failing requests. If successful, this would allow the attacker to impersonate the SCIM client for its abilities to read and update user accounts in the Zulip organization. Organizations where SCIM account management has not been enabled are not affected.

References

• https://github.com/zulip/zulip/security/advisories/GHSA-q5gx-377v-w76f
• https://github.com/zulip/zulip/commit/59edbfa4113d140d3e20126bc65f4d67b2a8ffe5