CVE-2021-20220

MEDIUMNVD 4.84.8—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 4.8 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 61% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
4.8
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 1%CVSS: 4.8Exploit: NoneExposed: 0

A fix is available — apply it.

A flaw was found in Undertow. A regression in the fix for CVE-2020-10687 was found. HTTP request smuggling related to CVE-2017-2666 is possible against HTTP/1.x and HTTP/2 due to permitting invalid characters in an HTTP request. This flaw allows an attacker to poison a web-cache, perform an XSS attack, or obtain sensitive information from request other than their own. The highest threat from this vulnerability is to data confidentiality and integrity.

CVSS v3
4.8
EG Score
4.8(medium)
EPSS
62.3%
KEV
Not listed

Published

February 23, 2021

Last Modified

November 21, 2024

References (4)

Patch Availability(4)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatwildfly-undertow2021-07-15redhat
redhateap7-wildfly-naming-client-0:1.0.14-1.Final_redhat_00001.1.el8eap2021-03-16redhat
redhateap7-wildfly-naming-client-0:1.0.14-1.Final_redhat_00001.1.el7eap2021-03-16redhat
redhateap7-wildfly-naming-client-0:1.0.14-1.Final_redhat_00001.1.el6eap2021-03-16redhat

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.

Affected Packages

(1 across 1 ecosystem)
Maven(1)
PackageVulnerable rangeFixed inDependents
io.undertow:undertow-core1.0.0.Alpha1 ... 2.0.9.Final (250 versions)2.0.34—

Weakness Classification(1)

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

All Vendor Advisories

(7)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 9× in last 7d / 47× 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. 2026-07-11 08:25 UTCEPSS rescore
  2. 2026-07-09 19:07 UTCEPSS rescore
  3. 2026-07-08 15:12 UTCEPSS rescore
  4. 2026-07-07 13:43 UTCEPSS rescore
  5. 2026-07-06 16:25 UTCEPSS rescore
  6. 2026-07-06 02:21 UTCEPSS rescore
  7. 2026-07-06 02:21 UTCEPSS rescore
  8. 2026-07-05 02:28 UTCEPSS rescore
  9. 2026-07-05 02:28 UTCEPSS rescore
  10. 2026-07-04 06:29 UTCEPSS rescore
  11. 2026-07-04 06:29 UTCEPSS rescore
  12. 2026-07-02 16:57 UTCEPSS rescore
  13. 2026-07-01 15:03 UTCEPSS rescore
  14. 2026-07-01 08:18 UTCOSV refresh
  15. 2026-06-30 23:20 UTCEPSS rescore
  16. 2026-06-30 23:20 UTCEPSS rescore
  17. 2026-06-29 14:04 UTCEPSS rescore
  18. 2026-06-29 14:04 UTCEPSS rescore
  19. 2026-06-28 14:05 UTCEPSS rescore
  20. 2026-06-28 04:54 UTCEPSS rescore
  21. 2026-06-28 04:54 UTCEPSS rescore
  22. 2026-06-27 03:06 UTCEPSS rescore
  23. 2026-06-27 03:06 UTCEPSS rescore
  24. 2026-06-25 13:48 UTCEPSS rescore
  25. 2026-06-25 13:48 UTCEPSS rescore
Show 59 more
  1. 2026-06-24 14:03 UTCEPSS rescore
  2. 2026-06-24 14:03 UTCEPSS rescore
  3. 2026-06-23 21:31 UTCEPSS rescore
  4. 2026-06-23 21:31 UTCEPSS rescore
  5. 2026-06-22 14:24 UTCEPSS rescore
  6. 2026-06-22 14:23 UTCEPSS rescore
  7. 2026-06-21 14:54 UTCEPSS rescore
  8. 2026-06-21 14:54 UTCEPSS rescore
  9. 2026-06-21 01:58 UTCEPSS rescore
  10. 2026-06-21 01:57 UTCEPSS rescore
  11. 2026-06-19 19:24 UTCEPSS rescore
  12. 2026-06-19 19:24 UTCEPSS rescore
  13. 2026-06-18 17:51 UTCEPSS rescore
  14. 2026-06-18 17:51 UTCEPSS rescore
  15. 2026-06-17 17:51 UTCEPSS rescore
  16. 2026-06-16 17:50 UTCEPSS rescore
  17. 2026-06-15 17:46 UTCEPSS rescore
  18. 2026-06-14 23:15 UTCEPSS rescore
  19. 2026-06-13 22:58 UTCEPSS rescore
  20. 2026-06-13 13:13 UTCOSV refresh
  21. 2026-06-12 23:10 UTCEPSS rescore
  22. 2026-06-12 23:10 UTCEPSS rescore
  23. 2026-06-11 13:58 UTCEPSS rescore
  24. 2026-06-10 22:16 UTCEPSS rescore
  25. 2026-06-10 22:16 UTCEPSS rescore
  26. 2026-06-10 13:20 UTCEPSS rescore
  27. 2026-06-08 14:15 UTCEPSS rescore
  28. 2026-06-08 14:15 UTCEPSS rescore
  29. 2026-06-07 15:23 UTCEPSS rescore
  30. 2026-06-07 15:23 UTCEPSS rescore
  31. 2026-06-06 13:46 UTCEPSS rescore
  32. 2026-06-06 13:46 UTCEPSS rescore
  33. 2026-06-06 13:46 UTCEPSS rescore
  34. 2026-06-05 22:45 UTCEPSS rescore
  35. 2026-06-05 22:45 UTCEPSS rescore
  36. 2026-06-05 06:09 UTCEPSS rescore
  37. 2026-06-05 06:09 UTCEPSS rescore
  38. 2026-06-05 06:08 UTCEPSS rescore
  39. 2026-06-04 13:10 UTCEPSS rescore
  40. 2026-06-02 20:11 UTCEPSS rescore
  41. 2026-06-02 20:11 UTCEPSS rescore
  42. 2026-06-01 13:50 UTCEPSS rescore
  43. 2026-06-01 13:50 UTCEPSS rescore
  44. 2026-05-31 22:29 UTCEPSS rescore
  45. 2026-05-31 22:29 UTCEPSS rescore
  46. 2026-05-31 00:15 UTCEPSS rescore
  47. 2026-05-31 00:15 UTCEPSS rescore
  48. 2026-05-29 13:42 UTCEPSS rescore
  49. 2026-05-28 13:43 UTCEPSS rescore
  50. 2026-05-28 13:43 UTCEPSS rescore
  51. 2026-05-27 13:39 UTCEPSS rescore
  52. 2026-05-26 20:31 UTCEG score recompute
  53. 2026-05-26 20:31 UTCVendor advisory
  54. 2026-05-26 13:42 UTCEPSS rescore
  55. 2026-05-26 13:42 UTCEPSS rescore
  56. 2026-05-26 07:17 UTCEPSS rescore
  57. 2026-05-26 07:17 UTCEPSS rescore
  58. 2026-05-24 16:49 UTCEPSS rescore
  59. 2026-05-23 09:31 UTCOSV refresh

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2021-20220?
CVE-2021-20220 is a medium vulnerability published on February 23, 2021. A flaw was found in Undertow. A regression in the fix for CVE-2020-10687 was found. HTTP request smuggling related to CVE-2017-2666 is possible against HTTP/1.x and HTTP/2 due to permitting invalid characters in an HTTP request. This flaw allows an attacker to poison a web-cache, perform an XSS…
When was CVE-2021-20220 disclosed?
CVE-2021-20220 was first published in the National Vulnerability Database on February 23, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-20220 actively exploited?
CVE-2021-20220 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 62.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-20220?
CVE-2021-20220 has a CVSS v3 base score of 4.8 (NVD).
How do I remediate CVE-2021-20220?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-20220, 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.

Dependency Blast Radius

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