CVE-2026-42581

CRITICALNVD 9.85.8▼
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.8 under NVD CVSS v3. EPSS exploit probability: 0.4%, top 67% 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
Elevated
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 9.8Exploit: NoneExposed: 0

A fix is available — apply it.

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, HttpObjectDecoder strips a conflicting Content-Length header when a request carries both Transfer-Encoding: chunked and Content-Length, but only for HTTP/1.1 messages. The guard is absent for HTTP/1.0. An attacker that sends an HTTP/1.0 request with both headers causes Netty to decode the body as chunked while leaving Content-Length intact in the forwarded HttpMessage. Any downstream proxy or handler that trusts Content-Length over Transfer-Encoding will disagree on message boundaries, enabling request smuggling. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

CVSS v3
9.8
EG Score
5.8(medium)
EPSS
45.4%
KEV
Not listed

Published

May 13, 2026

Last Modified

July 21, 2026

Advisory Details (10)

Auto-updated Jul 16, 2026
🔬 Proof of concept available. Patch available. Sources: github, redhat.
github Patch Available🟡 PoC Available

HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization · Advisory · netty/netty · GitHub

https://github.com/netty/netty/security/advisories/GHSA-xxqh-mfjm-7mv9
redhat Patch Available

2477232 – (CVE-2026-42581) CVE-2026-42581 netty: io.netty/netty-codec-http: Netty: HTTP Request Smuggling due to improper handling of conflicting HTTP/1.0 headers

https://bugzilla.redhat.com/show_bug.cgi?id=2477232
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2026-42581
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:37390
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:36820
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:28010
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:25123
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:24502
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:23808
redhat Patch Available
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42581.json

Vendor Advisories for CVE-2026-42581(7)

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

Patch Availability(5)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulibnetty-java (1:3.2.6.Final-2+deb8u2ubuntu0.1~esm1) @ trusty2026-06-29ubuntu
redhatcryostat/jfr-datasource-rhel9:4.2.0-102026-06-22redhat
redhatnetty-codec-http2026-06-10redhat
redhatpatch2026-06-10redhat
redhatdevspaces/server-rhel9:17806949942026-06-10redhat

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.netty:netty-codec-http4.0.0.Alpha1 ... 4.1.99.Final (226 versions)4.1.133.Final—

Weakness Classification(1)

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

Additional Vendor Advisories

(1)

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 8× in last 7d / 43× 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 14:08 UTCEPSS rescore
  2. 2026-07-21 15:24 UTCEPSS rescore
  3. 2026-07-20 17:08 UTCEPSS rescore
  4. 2026-07-19 14:31 UTCEPSS rescore
  5. 2026-07-19 02:29 UTCEPSS rescore
  6. 2026-07-18 10:04 UTCEPSS rescore
  7. 2026-07-18 02:29 UTCOSV refresh
  8. 2026-07-16 17:03 UTCEPSS rescore
  9. 2026-07-15 16:57 UTCEPSS rescore
  10. 2026-07-15 02:25 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  11. 2026-07-15 02:00 UTCEPSS rescore
  12. 2026-07-15 01:21 UTCMITRE cvelistV5CVSS v3 → 5.8 · severity → MEDIUM
  13. 2026-07-13 22:30 UTCEPSS rescore
  14. 2026-07-13 06:13 UTCEPSS rescore
  15. 2026-07-12 05:46 UTCEPSS rescore
  16. 2026-07-11 08:27 UTCEPSS rescore
  17. 2026-07-10 12:26 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  18. 2026-07-10 12:12 UTCMITRE cvelistV5CVSS v3 → 5.8 · severity → MEDIUM
  19. 2026-07-09 19:10 UTCEPSS rescore
  20. 2026-07-09 13:52 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  21. 2026-07-09 12:25 UTCMITRE cvelistV5CVSS v3 → 5.8 · severity → MEDIUM
  22. 2026-07-08 15:15 UTCEPSS rescore
  23. 2026-07-07 13:46 UTCEPSS rescore
  24. 2026-07-06 16:27 UTCEPSS rescore
  25. 2026-07-06 16:27 UTCEPSS rescore
Show 74 more
  1. 2026-07-06 02:23 UTCEPSS rescore
  2. 2026-07-06 02:23 UTCEPSS rescore
  3. 2026-07-05 02:30 UTCEPSS rescore
  4. 2026-07-04 06:31 UTCEPSS rescore
  5. 2026-07-01 15:06 UTCEPSS rescore
  6. 2026-06-30 23:22 UTCEPSS rescore
  7. 2026-06-30 04:33 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  8. 2026-06-29 22:13 UTCVendor advisory
  9. 2026-06-28 14:07 UTCEPSS rescore
  10. 2026-06-28 04:56 UTCEPSS rescore
  11. 2026-06-27 23:23 UTCVendor advisory
  12. 2026-06-27 03:08 UTCEPSS rescore
  13. 2026-06-26 20:46 UTCVendor advisory
  14. 2026-06-25 19:35 UTCVendor advisory
  15. 2026-06-25 13:49 UTCEPSS rescore
  16. 2026-06-25 13:49 UTCEPSS rescore
  17. 2026-06-24 14:05 UTCEPSS rescore
  18. 2026-06-23 21:33 UTCEPSS rescore
  19. 2026-06-22 14:25 UTCEPSS rescore
  20. 2026-06-22 14:25 UTCEPSS rescore
  21. 2026-06-21 14:56 UTCEPSS rescore
  22. 2026-06-21 14:56 UTCEPSS rescore
  23. 2026-06-21 01:59 UTCEPSS rescore
  24. 2026-06-19 19:25 UTCEPSS rescore
  25. 2026-06-18 17:52 UTCEPSS rescore
  26. 2026-06-18 17:52 UTCEPSS rescore
  27. 2026-06-17 17:53 UTCEPSS rescore
  28. 2026-06-17 04:20 UTCVendor advisory
  29. 2026-06-16 17:52 UTCEPSS rescore
  30. 2026-06-16 02:52 UTCVendor advisory
  31. 2026-06-15 17:49 UTCEPSS rescore
  32. 2026-06-15 01:02 UTCVendor advisory
  33. 2026-06-13 23:43 UTCVendor advisory
  34. 2026-06-13 23:00 UTCEPSS rescore
  35. 2026-06-12 23:12 UTCEPSS rescore
  36. 2026-06-12 23:12 UTCEPSS rescore
  37. 2026-06-12 19:26 UTCVendor advisory
  38. 2026-06-11 17:59 UTCVendor advisory
  39. 2026-06-11 14:00 UTCEPSS rescore
  40. 2026-06-10 22:18 UTCEPSS rescore
  41. 2026-06-10 16:47 UTCVendor advisory
  42. 2026-06-10 13:22 UTCEPSS rescore
  43. 2026-06-10 13:22 UTCEPSS rescore
  44. 2026-06-09 15:35 UTCVendor advisory
  45. 2026-06-08 14:17 UTCEPSS rescore
  46. 2026-06-08 14:17 UTCEPSS rescore
  47. 2026-06-07 15:25 UTCEPSS rescore
  48. 2026-06-07 15:25 UTCEPSS rescore
  49. 2026-06-06 13:47 UTCEPSS rescore
  50. 2026-06-06 13:47 UTCEPSS rescore
  51. 2026-06-05 22:47 UTCEPSS rescore
  52. 2026-06-04 13:12 UTCEPSS rescore
  53. 2026-06-04 13:12 UTCEPSS rescore
  54. 2026-06-02 20:13 UTCEPSS rescore
  55. 2026-06-01 13:52 UTCEPSS rescore
  56. 2026-06-01 13:52 UTCEPSS rescore
  57. 2026-05-31 22:30 UTCEPSS rescore
  58. 2026-05-31 22:30 UTCEPSS rescore
  59. 2026-05-31 00:16 UTCEPSS rescore
  60. 2026-05-31 00:16 UTCEPSS rescore
  61. 2026-05-29 13:44 UTCEPSS rescore
  62. 2026-05-29 13:44 UTCEPSS rescore
  63. 2026-05-28 13:44 UTCEPSS rescore
  64. 2026-05-28 13:44 UTCEPSS rescore
  65. 2026-05-27 13:40 UTCEPSS rescore
  66. 2026-05-27 13:40 UTCEPSS rescore
  67. 2026-05-26 13:44 UTCEPSS rescore
  68. 2026-05-26 07:18 UTCEPSS rescore
  69. 2026-05-26 07:18 UTCEPSS rescore
  70. 2026-05-20 22:38 UTCEPSS rescore
  71. 2026-05-20 22:38 UTCEPSS rescore
  72. 2026-05-20 12:26 UTCEG score recompute
  73. 2026-05-20 11:22 UTCEPSS rescore
  74. 2026-05-20 11:22 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-42581?
CVE-2026-42581 is a critical vulnerability published on May 13, 2026. Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, HttpObjectDecoder strips a conflicting Content-Length header when a request carries both Transfer-Encoding: chunked and Content-Length, but only for HTTP/1.1 messages. The guard is absent…
When was CVE-2026-42581 disclosed?
CVE-2026-42581 was first published in the National Vulnerability Database on May 13, 2026, with the most recent update on July 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-42581 actively exploited?
CVE-2026-42581 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 45.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-42581?
CVE-2026-42581 has a CVSS v3 base score of 9.8 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 5.8.
How do I remediate CVE-2026-42581?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42581, 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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