Bugsink vulnerable to unauthenticated remote DoS via crafted Brotli input

published 2025-11-10 11 mo ago modified 2026-07-07 4 mo ago also GHSA-fc2v-vcwj-269v , PYSEC-2026-1225 , EUVD-2025-50818

cvss: 7.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 43%
public exploits: 0; none known

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.

Patch / fix

fixed in 1 links 5

pypi bugsink 2.0.5

github.com/bugsink/bugsink@3f65544 commit
github.com/google/brotli@67d78bc commit
github.com/bugsink/bugsink#266 pull request
github.com/google/brotli#1234 pull request
github.com/google/brotli/releases/tag/v1.2.0 release

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: partial
Assessed: 11 mo ago (2025-11-12)

Exploit prediction

0.51% chance of exploitation in the next 30 days, higher than 43% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem	package	affected	fixed in
pypi	bugsink	<2.0.5	2.0.5

Affected products

bugsink bugsink

Classification

Weakness

CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary