CVE-2020-7212
Description
The _encode_invalid_chars 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 percent_encodings array contains all matches of percent encodings. It is not deduplicated. For a URL of length N, the size of percent_encodings 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 percent_encodings were deduplicated, the time to compute _encode_invalid_chars would be O(kN), where k is at most 484 ((10+6*2)^2).
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
OS impact
Debian Fixed 5 releases
| Version | Status | Fixed in |
|---|---|---|
| trixie | Fixed | 1.25.8-1 |
| sid | Fixed | 1.25.8-1 |
| forky | Fixed | 1.25.8-1 |
| bullseye | Fixed | 1.25.8-1 |
| bookworm | Fixed | 1.25.8-1 |
References
- https://nvd.nist.gov/vuln/detail/CVE-2020-7212
- https://github.com/urllib3/urllib3/commit/a74c9cfbaed9f811e7563cfc3dce894928e0221a
- https://github.com/advisories/GHSA-hmv2-79q8-fv6g
- https://github.com/pypa/advisory-database/tree/main/vulns/urllib3/PYSEC-2020-149.yaml
- https://github.com/urllib3/urllib3
- https://github.com/urllib3/urllib3/blob/master/CHANGES.rst
- https://pypi.org/project/urllib3/1.25.8
- https://pypi.org/project/urllib3/1.25.8/
- https://security-tracker.debian.org/tracker/CVE-2020-7212
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.