CVE-2026-53954 is a medium-severity (CVSS 4.3) Uncontrolled Resource Consumption vulnerability in bugsink. A fix is available for bugsink — see the affected versions and patch details below.
Bugsink: DOS using large numbers of event tags
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-53954.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-53954 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 390,807 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
bugsinkReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
In affected versions, Bugsink stores every tag supplied with an incoming event. An event with an unusually large number of custom (i.e. supplied by an attacker) tags can therefore make ingestion spend more time than intended writing tag rows.
Bugsink uses a single-writer database architecture. That keeps the implementation simple, but it also means one expensive write transaction can delay other event digestion while it is running. In this case, it makes ingestion of other events wait until the transaction that writes the tags finishes, which effectively causes a temporary denial of service for other events.
Impact
Submitting such an event requires a valid project DSN. DSNs are sometimes visible in client-side applications, so they should not be treated as a strong security boundary, but the issue is still limited to ingestion for a Bugsink instance that accepts the event.
The impact is availability-only. The issue does not expose stored data, modify existing events, or allow code execution.
Mitigation
Update to version 2.2.2, which caps the number of tags stored for a single event. The default cap is 100 tags and can
be changed with MAX_EVENT_TAGS.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | bugsink | all versions | 2.2.2pip install --upgrade 'bugsink==2.2.2' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for bugsink, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update bugsink to 2.2.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-53954 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is CVE-2026-53954 in your dependencies?
Find it across PyPI, including transitive dependencies.