CVE-2021-43797

MEDIUMNVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.5 under NVD CVSS v3. EPSS exploit probability: 2.9% (86th percentile of EPSS-scored CVEs). 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
Trending — 3 sources updated this week
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 2.9%CVSS: 6.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. Netty prior to version 4.1.71.Final skips control chars when they are present at the beginning / end of the header name. It should instead fail fast as these are not allowed by the spec and could lead to HTTP request smuggling. Failing to do the validation might cause netty to "sanitize" header names before it forward these to another remote system when used as proxy. This remote system can't see the invalid usage anymore, and therefore does not do the validation itself. Users should upgrade to version 4.1.71.Final.

CVSS v3
6.5
EG Score
6.5MEDIUMmedium confidence
EG Risk
30
EG Risk 30/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity65% × 45%
Exploitation3% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
2.9%
EPSS %ILE
86th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

December 9, 2021

Last Modified

October 8, 2026

Advisory Details (5)

Auto-updated Oct 8, 2026
Patch available. Sources: github, github_commit.
generic

[SECURITY] [DSA 5316-1] netty security update

https://www.debian.org/security/2023/dsa-5316
genericMentions a patch (unverified)

[SECURITY] [DLA 3268-1] netty security update

https://lists.debian.org/debian-lts-announce/2023/01/msg00008.html
generic

NetApp Product Security

https://security.netapp.com/advisory/ntap-20220107-0003/
github_commit Patch Available

commit 07aa6b5938a8 (netty/netty)

Patch available: netty/netty netty-4.1.132.Final (contains commit 07aa6b5938a8)

https://github.com/netty/netty/commit/07aa6b5938a8b6ed7a6586e066400e2643897323
githubMentions a patch (unverified)

HTTP fails to validate against control chars in header names which may lead to HTTP request smuggling · Advisory · netty/netty · GitHub

https://github.com/netty/netty/security/advisories/GHSA-wx5j-54mm-rqqq

Vendor Advisories for CVE-2021-43797(19)

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

Patch Availability(14)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibnetty-java (1:4.1.48-5ubuntu0.1) @ kinetic2026-10-08ubuntu
redhatrh-sso7-keycloak-0:18.0.3-1.redhat_00001.1.el8sso2022-11-03redhat
redhatrh-sso7-keycloak-0:18.0.3-1.redhat_00001.1.el9sso2022-11-03redhat
redhatnetty2022-11-03redhat
redhatrh-sso7-keycloak-0:18.0.3-1.redhat_00001.1.el7sso2022-11-03redhat
redhatrh-sso7-keycloak-0:15.0.8-1.redhat_00001.1.el8sso2022-10-04redhat
redhatrh-sso7-keycloak-0:15.0.8-1.redhat_00001.1.el7sso2022-10-04redhat
redhatcandlepin-0:4.1.13-1.el8sat2022-07-05redhat
redhatio.netty/netty-codec-http:4.1.72.Final-redhat-000012022-06-06redhat
redhateap7-netty-0:4.1.72-4.Final_redhat_00001.1.el7eap2022-06-06redhat
redhateap7-netty-0:4.1.72-4.Final_redhat_00001.1.el8eap2022-06-06redhat
redhatopenshift-logging/elasticsearch6-rhel8:v6.8.1-1562022-05-11redhat
redhatopenshift-logging/elasticsearch6-rhel8:v6.8.1-1592022-05-11redhat
redhatopenshift-logging/elasticsearch6-rhel8:v6.8.1-1572022-05-11redhat

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

(8 across 6 ecosystems)
Maven(3)
PackageVulnerable rangeFix by version rangeDependents
io.netty:netty3.10.0.Final ... 4.0.0.Alpha8 (71 versions)
  • every version on: no fix on record
—
io.netty:netty-codec-http4.0.0.Final ... 4.1.9.Final (144 versions)
  • 4.0.0 up to 4.1.71.Final: fixed in 4.1.71.Final
—
org.jboss.netty:netty3.0.0.CR1 ... 3.2.9.Final (39 versions)
  • every version on: no fix on record
—
Debian:10(1)
PackageVulnerable rangeFix by version rangeDependents
netty1:4.1.33-1, 1:4.1.33-1+deb10u1, 1:4.1.33-1+deb10u2
  • every version up to 1:4.1.33-1+deb10u3: fixed in 1:4.1.33-1+deb10u3
—
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
netty1:4.1.48-4
  • every version up to 1:4.1.48-4+deb11u1: fixed in 1:4.1.48-4+deb11u1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
netty—
  • every version up to 1:4.1.48-6: fixed in 1:4.1.48-6
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
netty—
  • every version up to 1:4.1.48-6: fixed in 1:4.1.48-6
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
netty—
  • every version up to 1:4.1.48-6: fixed in 1:4.1.48-6
—

Weakness Classification(1)

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

Additional Vendor Advisories

(2)

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 / 34× 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.

Showing the most recent 100 of 191 total refreshes for this CVE.

  1. 2026-10-09 20:04 UTCEPSS rescore
  2. 2026-10-08 22:27 UTCVendor advisory
  3. 2026-10-08 21:32 UTCEG score recompute
  4. 2026-10-08 21:32 UTCVendor advisory
  5. 2026-10-08 16:40 UTCEPSS rescore
  6. 2026-10-07 23:45 UTCEPSS rescore
  7. 2026-10-06 15:14 UTCEPSS rescore
  8. 2026-10-05 17:40 UTCEPSS rescore
  9. 2026-10-03 14:22 UTCEPSS rescore
  10. 2026-10-02 16:23 UTCEPSS rescore
  11. 2026-10-01 19:46 UTCEPSS rescore
  12. 2026-09-30 15:43 UTCEG score recompute
  13. 2026-09-30 15:00 UTCEPSS rescore
  14. 2026-09-29 15:15 UTCEPSS rescore
  15. 2026-09-28 13:47 UTCEPSS rescore
  16. 2026-09-27 13:41 UTCEPSS rescore
  17. 2026-09-26 15:54 UTCEPSS rescore
  18. 2026-09-26 00:21 UTCEPSS rescore
  19. 2026-09-25 10:36 UTCOSV refresh
  20. 2026-09-24 14:00 UTCEPSS rescore
  21. 2026-09-24 14:00 UTCEPSS rescore
  22. 2026-09-23 13:44 UTCEPSS rescore
  23. 2026-09-22 14:44 UTCEPSS rescore
  24. 2026-09-21 20:28 UTCEPSS rescore
  25. 2026-09-20 20:13 UTCEPSS rescore
Show 75 more
  1. 2026-09-19 15:38 UTCEPSS rescore
  2. 2026-09-18 19:23 UTCEPSS rescore
  3. 2026-09-17 19:23 UTCEPSS rescore
  4. 2026-09-17 19:23 UTCEPSS rescore
  5. 2026-09-16 14:05 UTCEPSS rescore
  6. 2026-09-15 03:06 UTCEPSS rescore
  7. 2026-09-12 14:57 UTCEPSS rescore
  8. 2026-09-11 14:49 UTCEPSS rescore
  9. 2026-09-11 09:33 UTCEPSS rescore
  10. 2026-09-08 21:56 UTCEPSS rescore
  11. 2026-09-07 15:58 UTCEPSS rescore
  12. 2026-09-06 13:45 UTCEPSS rescore
  13. 2026-09-06 02:00 UTCOSV refresh
  14. 2026-09-05 15:25 UTCEPSS rescore
  15. 2026-09-04 13:57 UTCEPSS rescore
  16. 2026-09-04 05:03 UTCEPSS rescore
  17. 2026-09-02 14:09 UTCEPSS rescore
  18. 2026-09-01 13:50 UTCEPSS rescore
  19. 2026-09-01 03:33 UTCEPSS rescore
  20. 2026-08-30 19:14 UTCEPSS rescore
  21. 2026-08-30 19:14 UTCEPSS rescore
  22. 2026-08-30 01:19 UTCEPSS rescore
  23. 2026-08-28 21:37 UTCEPSS rescore
  24. 2026-08-27 14:22 UTCEPSS rescore
  25. 2026-08-26 14:43 UTCEPSS rescore
  26. 2026-08-25 13:46 UTCEPSS rescore
  27. 2026-08-24 14:13 UTCEPSS rescore
  28. 2026-08-23 00:16 UTCEPSS rescore
  29. 2026-08-21 23:46 UTCEPSS rescore
  30. 2026-08-20 22:52 UTCEPSS rescore
  31. 2026-08-20 22:52 UTCEPSS rescore
  32. 2026-08-19 17:01 UTCEPSS rescore
  33. 2026-08-19 13:29 UTCOSV refresh
  34. 2026-08-18 13:45 UTCEPSS rescore
  35. 2026-08-17 13:44 UTCEPSS rescore
  36. 2026-08-16 14:53 UTCEPSS rescore
  37. 2026-08-16 02:11 UTCEPSS rescore
  38. 2026-08-15 01:27 UTCEPSS rescore
  39. 2026-08-13 21:57 UTCEPSS rescore
  40. 2026-08-12 13:48 UTCEPSS rescore
  41. 2026-08-11 13:38 UTCEPSS rescore
  42. 2026-08-09 13:44 UTCEPSS rescore
  43. 2026-08-08 16:33 UTCEPSS rescore
  44. 2026-08-07 16:24 UTCEPSS rescore
  45. 2026-08-06 13:44 UTCEPSS rescore
  46. 2026-08-05 19:14 UTCEPSS rescore
  47. 2026-08-04 10:34 UTCEPSS rescore
  48. 2026-08-04 08:57 UTCOSV refresh
  49. 2026-08-03 10:33 UTCEPSS rescore
  50. 2026-08-02 02:24 UTCEPSS rescore
  51. 2026-08-01 04:13 UTCEPSS rescore
  52. 2026-07-30 16:25 UTCEPSS rescore
  53. 2026-07-30 01:28 UTCEPSS rescore
  54. 2026-07-28 15:33 UTCEPSS rescore
  55. 2026-07-26 14:52 UTCEPSS rescore
  56. 2026-07-26 14:52 UTCEPSS rescore
  57. 2026-07-25 14:15 UTCEPSS rescore
  58. 2026-07-24 14:15 UTCEPSS rescore
  59. 2026-07-23 14:16 UTCEPSS rescore
  60. 2026-07-23 02:05 UTCEG score recompute
  61. 2026-07-22 22:51 UTCEG score recompute
  62. 2026-07-22 14:06 UTCEPSS rescore
  63. 2026-07-21 15:22 UTCEPSS rescore
  64. 2026-07-21 15:22 UTCEPSS rescore
  65. 2026-07-20 17:05 UTCEPSS rescore
  66. 2026-07-19 14:29 UTCEPSS rescore
  67. 2026-07-19 02:27 UTCEPSS rescore
  68. 2026-07-18 10:02 UTCEPSS rescore
  69. 2026-07-18 10:02 UTCEPSS rescore
  70. 2026-07-18 06:29 UTCOSV refresh
  71. 2026-07-16 17:00 UTCEPSS rescore
  72. 2026-07-16 17:00 UTCEPSS rescore
  73. 2026-07-15 16:55 UTCEPSS rescore
  74. 2026-07-15 16:55 UTCEPSS rescore
  75. 2026-07-15 01:58 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2021-43797?
CVE-2021-43797 is a medium vulnerability published on December 9, 2021. Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. Netty prior to version 4.1.71.Final skips control chars when they are present at the beginning / end of the header name. It should instead fail fast…
When was CVE-2021-43797 disclosed?
CVE-2021-43797 was first published on December 9, 2021, with the most recent update on October 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-43797 actively exploited?
CVE-2021-43797 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 2.9% probability of exploitation in the next 30 days (86th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2021-43797?
CVE-2021-43797 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2021-43797?
A fix for CVE-2021-43797 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2021-43797 are linked in the Vendor Advisories panel on this page.

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