Uncontrolled Resource Consumption in urllib3

Exploitation

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

CVSS 4.0

8.7 · 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 · score source

EPSS

• CVE-2020-7212: 3.37% estimated exploitation activity in the next 30 days; percentile 88.77 (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.

The encodeinvalidchars function in util/url.py in the urllib3 library 1.25.2 through 1.25.7 for Python allows a denial of service (CPU consumption) because of an inefficient algorithm. The percentencodings array contains all matches of percent encodings. It is not deduplicated. For a URL of length N, the size of percentencodings may be up to O(N). The next step (normalize existing percent-encoded bytes) also takes up to O(N) for each step, so the total time is O(N^2). If percentencodings were deduplicated, the time to compute encodeinvalidchars would be O(kN), where k is at most 484 ((10+62)^2).

Published by the source

30 Apr 2021, 17:31 UTC

Last modified by the source

18 Nov 2024, 22:35 UTC

Source last checked

26 Oct 2026, 13:27 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-hmv2-79q8-fv6g

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-hmv2-79q8-fv6g

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# Patch Next advisory brief: CVE-2020-7212

Advisory: Uncontrolled Resource Consumption in urllib3
IDs: CVE-2020-7212, GHSA-hmv2-79q8-fv6g
Record: https://patchnext.com/advisories/cve-2020-7212 (revision 3, source checked 26 Oct 2026, 13:27 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: urllib3 1.25.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI urllib3: affected >= 1.25.2, <= 1.25.7; fixed in 1.25.8

## Suggested inspection (read-only)
- `python -m pip show urllib3`: 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 urllib3.
- 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-hmv2-79q8-fv6g (OSV record GHSA-hmv2-79q8-fv6g lists affected ranges: PyPI urllib3 >=1.25.2 <1.25.8 (fixed))
- Verified: https://github.com/advisories/GHSA-hmv2-79q8-fv6g (GitHub-reviewed advisory GHSA-hmv2-79q8-fv6g lists affected ranges: PyPI urllib3 >=1.25.2 <=1.25.7)

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