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MEDIUM severity

Bunsink has an SSRF bypass in `validate_webhook_url`GHSA-fp53-qcf8-2xx2

MEDIUMFix: bugsink/bugsink@940d2df

GHSA-fp53-qcf8-2xx2 is a medium-severity (CVSS 4.3) Server-Side Request Forgery (SSRF) vulnerability in bugsink. A fix is available for bugsink — see the affected versions and patch details below.

Also known asCVE-2026-44502PYSEC-2026-2405
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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 GHSA-fp53-qcf8-2xx2.

EPSS Exploitation Probability

via FIRST.org ↗
0.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs21th percentile — riskier than 21% of all scored CVEsHighest risk
0.00%0.30%0.59%0.89%0.0%0.3%Jun 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐍bugsink

Real-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

Bugsink’s webhook URL validation in versions 2.1.2 and earlier could be (partially) bypassed because of a mismatch in URL parsing.

In some malformed URLs, Python’s standard URL parser (urllib) and the HTTP client stack (requests / urllib3) do not agree on which host is actually being targeted. That could allow a webhook URL to pass Bugsink’s outbound-host checks while the actual HTTP request is sent somewhere else.

Impact

This issue affects Bugsink’s outbound webhook integrations.

An attacker who can supply or influence a webhook URL may be able to make Bugsink send an outbound HTTP POST request to a host that should have been blocked by the webhook validation logic, including loopback, private, or otherwise non-allowlisted destinations.

The practical impact is limited:

  • this is an outbound webhook SSRF issue, not a general-purpose proxy
  • Bugsink does not follow redirects for these webhook requests
  • the request shape is constrained by how the malformed URL is normalized by the HTTP client
  • this does not give arbitrary control over every possible request path

In other words, this is a real validation bypass, but it is narrower than a full arbitrary-request primitive.

Technical Details

The original validation logic parsed webhook URLs with Python’s urllib.parse.urlparse, then sent the request with requests.post.

For malformed inputs involving backslashes and @, those components can disagree about where the authority ends and which hostname is the real target. A URL may therefore appear to target an allowlisted public hostname during validation, while the HTTP client actually connects to a different host.

Fix

The fix has two parts:

  1. Bugsink now normalizes webhook URLs using the same HTTP client stack that will later send them, and applies validation to that normalized form.
  2. Bugsink now outright rejects raw webhook URLs containing characters outside the RFC URL character set, rather than relying on downstream normalization of malformed input.

Together, these changes remove the parser discrepancy and make webhook URL handling stricter and more predictable.

Workarounds

If users cannot upgrade immediately:

  • restrict who can configure or modify webhook URLs
  • review existing webhook configurations for malformed or unusual URLs
  • prefer tightly controlled outbound network policy at the deployment level

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIbugsinkall versions2.1.3pip install --upgrade 'bugsink==2.1.3'

Detection & mitigation playbook

Open-source dependency

  1. Detect

    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.

  2. Fix

    Update bugsink to 2.1.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fp53-qcf8-2xx2 is resolved across your whole dependency graph.

  3. Workarounds

    Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Frequently Asked Questions

## Summary Bugsink’s webhook URL validation in versions 2.1.2 and earlier could be (partially) bypassed because of a mismatch in URL parsing. In some malformed URLs, Python’s standard URL parser (urllib) and the HTTP client stack (requests / urllib3) do not agree on which host is actually being targeted. That could allow a webhook URL to pass Bugsink’s outbound-host checks while the actual HTTP request is sent somewhere else. ## Impact This issue affects Bugsink’s outbound webhook integrations. An attacker who can supply or influence a webhook URL may be able to make Bugsink send an outb
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Bunsink has an SSRF bypass in `validate_webhook_url`