CVE-2025-64509 Bugsink vulnerable to unauthenticated remote DoS via crafted Brotli input (via CPU)
An attacker can cause denial of service in Bugsink by sending crafted Brotli input, consuming excessive CPU resources.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-64509?
CVE-2025-64509 is a high-severity denial of service vulnerability in bugsink, published on 10 Nov 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Bugsink is a self-hosted error tracking tool. In versions prior to 2.0.6, a specially crafted Brotli-compressed envelope can cause Bugsink to spend excessive CPU time in decompression, leading to denial of service. This can be done if the DSN is known, which it is in many common setups (JavaScript, Mobile Apps). The issue is patched in Bugsink 2.0.6. The vulnerability is similar to, but distinct from, another brotli-related problem in Bugsink, GHSA-fc2v-vcwj-269v/CVE-2025-64508.
Weakness: CWE-770
Which versions are affected by CVE-2025-64509?
3 open source packages ship an affected version, including bugsink.
| Package | Affected | Fixed in |
|---|---|---|
bugsink PyPI | All versions | 2.0.6 |
bugsink PyPI | All versions | 2.0.6 |
bugsink PyPI | All versions | 2.0.6 |
How do I fix CVE-2025-64509?
Upgrade bugsink to 2.0.6 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-64509 being exploited?
There is no known exploitation of CVE-2025-64509 in the wild and no public exploit code.
Sources
Also known as GHSA-rrx3-2x4g-mq2h, PYSEC-2026-1227.