The Markdown parser in Zulip server before 2.0.5 used a regular expression vulnerable to exponential backtracking. A user who is logged into the server could send a crafted message causing the server to spend an effectively arbitrary amount of CPU time and stall the processing of future messages.
The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Zulip_server | Zulip | * | 2.0.5 (excluding) |
Attackers can create crafted inputs that
intentionally cause the regular expression to use
excessive backtracking in a way that causes the CPU
consumption to spike.