CVE-2021-23336

MEDIUMNVD 5.95.9—
EchelonGraph scoreMEDIUM confidence

Score 5.9 from GitHub Security Advisory (severity: HIGH) published 2022-02-08. NVD baseline CVSS 5.9; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 3 sources updated this weekElevated
5.9
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 36%CVSS: 5.9Exploit: NoneExposed: 0

A fix is available — apply it.

The package python/cpython from 0 and before 3.6.13, from 3.7.0 and before 3.7.10, from 3.8.0 and before 3.8.8, from 3.9.0 and before 3.9.2 are vulnerable to Web Cache Poisoning via urllib.parse.parse_qsl and urllib.parse.parse_qs by using a vector called parameter cloaking. When the attacker can separate query parameters using a semicolon (;), they can cause a difference in the interpretation of the request between the proxy (running with default configuration) and the server. This can result in malicious requests being cached as completely safe ones, as the proxy would usually not see the semicolon as a separator, and therefore would not include it in a cache key of an unkeyed parameter.

CVSS v3
5.9
EG Score
5.9(medium)
EG Risk
—
EPSS
98.3%
KEV
Not listed

Published

February 15, 2021

Last Modified

December 17, 2025

References (74)

Vendor Advisories for CVE-2021-23336(3)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(6)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntupython3-django (2:2.2.16-1ubuntu0.2) @ groovy2026-05-26ubuntu
redhatpython27:2.7-8050020210811095446.3e7ace8b2021-11-09redhat
redhatpython38-devel:3.8-8050020210811101222.e3d35cca2021-11-09redhat
redhatpython27-python-pygments-0:1.5-5.el72021-08-24redhat
redhatrh-python38-python-urllib3-0:1.25.7-7.el72021-08-24redhat
redhatpython3-0:3.6.8-37.el82021-05-18redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(4)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 9× in last 7d / 41× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-22 22:44 UTCEG score recompute
  2. 2026-07-22 14:05 UTCEPSS rescore
  3. 2026-07-21 15:22 UTCEPSS rescore
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  5. 2026-07-20 17:04 UTCEPSS rescore
  6. 2026-07-19 14:28 UTCEPSS rescore
  7. 2026-07-19 01:29 UTCOSV refresh
  8. 2026-07-18 10:02 UTCEPSS rescore
  9. 2026-07-16 17:00 UTCEPSS rescore
  10. 2026-07-15 16:55 UTCEPSS rescore
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  1. 2026-07-05 02:28 UTCEPSS rescore
  2. 2026-07-02 16:57 UTCEPSS rescore
  3. 2026-07-01 15:03 UTCEPSS rescore
  4. 2026-07-01 08:48 UTCOSV refresh
  5. 2026-06-29 14:04 UTCEPSS rescore
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  7. 2026-06-28 04:54 UTCEPSS rescore
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  22. 2026-06-16 17:50 UTCEPSS rescore
  23. 2026-06-15 17:46 UTCEPSS rescore
  24. 2026-06-14 23:15 UTCEPSS rescore
  25. 2026-06-13 22:58 UTCEPSS rescore
  26. 2026-06-13 13:43 UTCOSV refresh
  27. 2026-06-12 23:10 UTCEPSS rescore
  28. 2026-06-12 23:10 UTCEPSS rescore
  29. 2026-06-11 13:58 UTCEPSS rescore
  30. 2026-06-10 22:16 UTCEPSS rescore
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  40. 2026-06-05 22:45 UTCEPSS rescore
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  42. 2026-06-05 06:09 UTCEPSS rescore
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  44. 2026-06-05 06:08 UTCEPSS rescore
  45. 2026-06-04 13:10 UTCEPSS rescore
  46. 2026-06-02 20:11 UTCEPSS rescore
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  48. 2026-06-01 13:50 UTCEPSS rescore
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  50. 2026-05-31 22:29 UTCEPSS rescore
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  52. 2026-05-31 00:15 UTCEPSS rescore
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  54. 2026-05-29 13:42 UTCEPSS rescore
  55. 2026-05-28 13:43 UTCEPSS rescore
  56. 2026-05-28 13:43 UTCEPSS rescore
  57. 2026-05-27 13:39 UTCEPSS rescore
  58. 2026-05-26 20:49 UTCEG score recompute
  59. 2026-05-26 20:49 UTCVendor advisory
  60. 2026-05-26 20:49 UTCGHSA enrichment
  61. 2026-05-26 13:42 UTCEPSS rescore
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  63. 2026-05-26 07:17 UTCEPSS rescore
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  65. 2026-05-24 16:49 UTCEPSS rescore

Frequently asked(5)

What is CVE-2021-23336?
CVE-2021-23336 is a medium vulnerability published on February 15, 2021. The package python/cpython from 0 and before 3.6.13, from 3.7.0 and before 3.7.10, from 3.8.0 and before 3.8.8, from 3.9.0 and before 3.9.2 are vulnerable to Web Cache Poisoning via urllib.parse.parseqsl and urllib.parse.parseqs by using a vector called parameter cloaking. When the attacker can…
When was CVE-2021-23336 disclosed?
CVE-2021-23336 was first published in the National Vulnerability Database on February 15, 2021, with the most recent update on December 17, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-23336 actively exploited?
CVE-2021-23336 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 98.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-23336?
CVE-2021-23336 has a CVSS v3 base score of 5.9 (NVD).
How do I remediate CVE-2021-23336?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-23336, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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