priority vulnerable to denial of service

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.6 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U · score source

EPSS

• CVE-2016-6580: 1.81% estimated exploitation activity in the next 30 days; percentile 78.60 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

A HTTP/2 implementation built using any version of the Python priority library prior to version 1.2.0 could be targeted by a malicious peer by having that peer assign priority information for every possible HTTP/2 stream ID. The priority tree would happily continue to store the priority information for each stream, and would therefore allocate unbounded amounts of memory. Attempting to actually use a tree like this would also cause extremely high CPU usage to maintain the tree.

Published by the source

17 May 2022, 03:02 UTC

Last modified by the source

30 Aug 2024, 23:58 UTC

Source last checked

26 Oct 2026, 13:16 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-h3q4-6j7f-r24c

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-h3q4-6j7f-r24c

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# Patch Next advisory brief: CVE-2016-6580

Advisory: priority vulnerable to denial of service
IDs: CVE-2016-6580, GHSA-h3q4-6j7f-r24c
Record: https://patchnext.com/advisories/cve-2016-6580 (revision 3, source checked 26 Oct 2026, 13:16 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: priority 1.2.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI priority: affected < 1.2.0; fixed in 1.2.0

## Suggested inspection (read-only)
- `python -m pip show priority`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on priority.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-h3q4-6j7f-r24c (OSV record GHSA-h3q4-6j7f-r24c lists affected ranges: PyPI priority >=0 <1.2.0 (fixed))
- Verified: https://github.com/advisories/GHSA-h3q4-6j7f-r24c (GitHub-reviewed advisory GHSA-h3q4-6j7f-r24c lists affected ranges: PyPI priority >=0 <1.2.0)

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