CVE-2026-59921

MEDIUMNVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.5 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 84% 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
Trending — 3 sources updated this weekElevated
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: Elevated riskExposed: 0

A fix is available — apply it.

Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, HttpPostRequestEncoder constructs multipart HTTP request bodies by directly concatenating user-supplied filenames and field names into Content-Disposition MIME headers without validating or sanitizing CRLF characters (\r\n). Since MIME headers are delimited by CRLF, an attacker who controls the filename can inject arbitrary MIME headers into the multipart body part. The root cause is that neither the encoder nor the FileUpload implementations' setFilename() methods, which only check for null, neutralize CRLF characters before the filename is embedded into the header. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.

CVSS v3
6.5
EG Score
6.5(medium)
EG Risk
45(Track)
EG Risk 45/100SSVC: Track

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%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
16%
KEV
Not listed

Published

July 22, 2026

Last Modified

August 7, 2026

Advisory Details (1)

Auto-updated Jul 28, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

CRLF Injection via Multipart Filename in Netty HttpPostRequestEncoder · Advisory · netty/netty · GitHub

https://github.com/netty/netty/security/advisories/GHSA-gcjf-9mgh-3p7g

Vendor Advisories for CVE-2026-59921(3)

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

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatnetty-codec-http2026-07-30redhat

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

(5 across 5 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
netty1:4.1.48-10 ... 1:4.1.48-9 (16 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
netty1:4.1.48-10 ... 1:4.1.48-9 (12 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
netty1:4.1.48-10 ... 1:4.1.48-16 (8 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
netty1:4.1.48-10 ... 1:4.1.48-16 (7 versions)——
Maven(1)
PackageVulnerable rangeFixed inDependents
io.netty:netty-codec-http4.0.0.Alpha1 ... 4.1.99.Final (229 versions)4.1.136.Final—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 14× in last 7d / 70× 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 131 total refreshes for this CVE.

  1. 2026-09-15 03:11 UTCEPSS rescore
  2. 2026-09-13 22:25 UTCEG score recompute
  3. 2026-09-13 22:25 UTCVendor advisory
  4. 2026-09-13 16:47 UTCEPSS rescore
  5. 2026-09-12 20:24 UTCEG score recompute
  6. 2026-09-12 20:24 UTCVendor advisory
  7. 2026-09-11 20:56 UTCEG score recompute
  8. 2026-09-11 20:56 UTCVendor advisory
  9. 2026-09-11 14:53 UTCEPSS rescore
  10. 2026-09-10 21:14 UTCEG score recompute
  11. 2026-09-10 21:14 UTCVendor advisory
  12. 2026-09-10 09:35 UTCEPSS rescore
  13. 2026-09-09 09:11 UTCEG score recompute
  14. 2026-09-09 09:11 UTCVendor advisory
  15. 2026-09-08 22:01 UTCEPSS rescore
  16. 2026-09-07 21:39 UTCEG score recompute
  17. 2026-09-07 21:39 UTCVendor advisory
  18. 2026-09-07 16:01 UTCEPSS rescore
  19. 2026-09-06 18:59 UTCEG score recompute
  20. 2026-09-06 18:59 UTCVendor advisory
  21. 2026-09-06 13:47 UTCEPSS rescore
  22. 2026-09-05 19:33 UTCEG score recompute
  23. 2026-09-05 19:33 UTCVendor advisory
  24. 2026-09-04 13:39 UTCEG score recompute
  25. 2026-09-04 13:39 UTCVendor advisory
Show 75 more
  1. 2026-09-04 05:07 UTCEPSS rescore
  2. 2026-09-02 14:12 UTCEPSS rescore
  3. 2026-09-01 23:36 UTCEG score recompute
  4. 2026-09-01 23:36 UTCVendor advisory
  5. 2026-09-01 13:54 UTCEPSS rescore
  6. 2026-09-01 04:40 UTCEPSS rescore
  7. 2026-08-31 00:16 UTCEG score recompute
  8. 2026-08-31 00:16 UTCVendor advisory
  9. 2026-08-30 19:17 UTCEPSS rescore
  10. 2026-08-30 01:22 UTCEPSS rescore
  11. 2026-08-30 00:50 UTCEG score recompute
  12. 2026-08-30 00:50 UTCVendor advisory
  13. 2026-08-28 21:42 UTCEPSS rescore
  14. 2026-08-28 04:29 UTCEG score recompute
  15. 2026-08-28 04:29 UTCVendor advisory
  16. 2026-08-27 14:25 UTCEPSS rescore
  17. 2026-08-27 04:54 UTCEG score recompute
  18. 2026-08-27 04:54 UTCVendor advisory
  19. 2026-08-26 14:46 UTCEPSS rescore
  20. 2026-08-26 04:40 UTCEG score recompute
  21. 2026-08-26 04:40 UTCVendor advisory
  22. 2026-08-25 13:49 UTCEPSS rescore
  23. 2026-08-25 05:10 UTCEG score recompute
  24. 2026-08-25 05:10 UTCVendor advisory
  25. 2026-08-24 05:45 UTCVendor advisory
  26. 2026-08-23 06:18 UTCEG score recompute
  27. 2026-08-23 06:18 UTCVendor advisory
  28. 2026-08-23 00:19 UTCEPSS rescore
  29. 2026-08-22 06:52 UTCEG score recompute
  30. 2026-08-22 06:52 UTCVendor advisory
  31. 2026-08-21 23:49 UTCEPSS rescore
  32. 2026-08-21 07:26 UTCEG score recompute
  33. 2026-08-21 07:26 UTCVendor advisory
  34. 2026-08-20 22:55 UTCEPSS rescore
  35. 2026-08-20 08:00 UTCEG score recompute
  36. 2026-08-20 08:00 UTCVendor advisory
  37. 2026-08-19 17:04 UTCEPSS rescore
  38. 2026-08-19 08:34 UTCEG score recompute
  39. 2026-08-19 08:34 UTCVendor advisory
  40. 2026-08-18 13:48 UTCEPSS rescore
  41. 2026-08-18 09:03 UTCEG score recompute
  42. 2026-08-18 09:03 UTCVendor advisory
  43. 2026-08-17 13:47 UTCEPSS rescore
  44. 2026-08-17 09:32 UTCEG score recompute
  45. 2026-08-17 09:32 UTCVendor advisory
  46. 2026-08-16 14:56 UTCEPSS rescore
  47. 2026-08-16 10:06 UTCEG score recompute
  48. 2026-08-16 10:06 UTCVendor advisory
  49. 2026-08-16 02:14 UTCEPSS rescore
  50. 2026-08-15 10:41 UTCEG score recompute
  51. 2026-08-15 10:41 UTCVendor advisory
  52. 2026-08-15 01:30 UTCEPSS rescore
  53. 2026-08-14 11:14 UTCEG score recompute
  54. 2026-08-14 11:14 UTCVendor advisory
  55. 2026-08-13 22:00 UTCEPSS rescore
  56. 2026-08-13 11:48 UTCEG score recompute
  57. 2026-08-13 11:48 UTCVendor advisory
  58. 2026-08-12 13:51 UTCEPSS rescore
  59. 2026-08-12 12:22 UTCEG score recompute
  60. 2026-08-12 12:22 UTCVendor advisory
  61. 2026-08-11 12:55 UTCEG score recompute
  62. 2026-08-11 12:55 UTCVendor advisory
  63. 2026-08-11 00:00 UTCEPSS rescore
  64. 2026-08-10 13:29 UTCVendor advisory
  65. 2026-08-09 13:59 UTCEG score recompute
  66. 2026-08-09 13:59 UTCVendor advisory
  67. 2026-08-09 13:46 UTCEPSS rescore
  68. 2026-08-08 16:37 UTCEPSS rescore
  69. 2026-08-08 14:34 UTCEG score recompute
  70. 2026-08-08 14:34 UTCVendor advisory
  71. 2026-08-07 15:07 UTCVendor advisory
  72. 2026-08-06 19:43 UTCEG score recompute▲ 0.80
  73. 2026-08-06 19:43 UTCVendor advisory
  74. 2026-08-06 19:43 UTCNVD updateCVSS v3 → 6.5
  75. 2026-08-06 13:52 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-59921?
CVE-2026-59921 is a medium vulnerability published on July 22, 2026. Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, HttpPostRequestEncoder constructs multipart HTTP request bodies by directly concatenating user-supplied filenames and field names into Content-Disposition MIME headers without…
When was CVE-2026-59921 disclosed?
CVE-2026-59921 was first published in the National Vulnerability Database on July 22, 2026, with the most recent update on August 7, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-59921 actively exploited?
CVE-2026-59921 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 84.0% of all scored CVEs.
What is the CVSS score of CVE-2026-59921?
CVE-2026-59921 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-59921?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-59921, 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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