CVE-2026-42581

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 0.6%, top 55% 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
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.8Exploit: Elevated riskExposed: 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
9.8(medium)
EG Risk
75(Attend)
EG Risk 75/100SSVC: Attend

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
Severity98% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
1%
EPSS %ILE
45%
KEV
Not listed

Published

May 13, 2026

Last Modified

July 21, 2026

Advisory Details (11)

Auto-updated Jul 25, 2026
🔬 Proof of concept available. Patch available. Sources: github, redhat.
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-2026:42644
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
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
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 10× 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.

Showing the most recent 100 of 106 total refreshes for this CVE.

  1. 2026-07-27 14:13 UTCEPSS rescore
  2. 2026-07-26 14:54 UTCEPSS rescore
  3. 2026-07-26 14:54 UTCEPSS rescore
  4. 2026-07-25 14:18 UTCEPSS rescore
  5. 2026-07-24 14:17 UTCEPSS rescore
  6. 2026-07-23 14:18 UTCEPSS rescore
  7. 2026-07-23 03:11 UTCEG score recompute▲ 4.00
  8. 2026-07-22 14:08 UTCEPSS rescore
  9. 2026-07-21 15:24 UTCEPSS rescore
  10. 2026-07-20 17:08 UTCEPSS rescore
  11. 2026-07-19 14:31 UTCEPSS rescore
  12. 2026-07-19 02:29 UTCEPSS rescore
  13. 2026-07-18 10:04 UTCEPSS rescore
  14. 2026-07-18 02:29 UTCOSV refresh
  15. 2026-07-16 17:03 UTCEPSS rescore
  16. 2026-07-15 16:57 UTCEPSS rescore
  17. 2026-07-15 02:25 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  18. 2026-07-15 02:00 UTCEPSS rescore
  19. 2026-07-15 01:21 UTCMITRE cvelistV5CVSS v3 → 5.8 · severity → MEDIUM
  20. 2026-07-13 22:30 UTCEPSS rescore
  21. 2026-07-13 06:13 UTCEPSS rescore
  22. 2026-07-12 05:46 UTCEPSS rescore
  23. 2026-07-11 08:27 UTCEPSS rescore
  24. 2026-07-10 12:26 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  25. 2026-07-10 12:12 UTCMITRE cvelistV5CVSS v3 → 5.8 · severity → MEDIUM
Show 75 more
  1. 2026-07-09 19:10 UTCEPSS rescore
  2. 2026-07-09 13:52 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  3. 2026-07-09 12:25 UTCMITRE cvelistV5CVSS v3 → 5.8 · severity → MEDIUM
  4. 2026-07-08 15:15 UTCEPSS rescore
  5. 2026-07-07 13:46 UTCEPSS rescore
  6. 2026-07-06 16:27 UTCEPSS rescore
  7. 2026-07-06 16:27 UTCEPSS rescore
  8. 2026-07-06 02:23 UTCEPSS rescore
  9. 2026-07-06 02:23 UTCEPSS rescore
  10. 2026-07-05 02:30 UTCEPSS rescore
  11. 2026-07-04 06:31 UTCEPSS rescore
  12. 2026-07-01 15:06 UTCEPSS rescore
  13. 2026-06-30 23:22 UTCEPSS rescore
  14. 2026-06-30 04:33 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  15. 2026-06-29 22:13 UTCVendor advisory
  16. 2026-06-28 14:07 UTCEPSS rescore
  17. 2026-06-28 04:56 UTCEPSS rescore
  18. 2026-06-27 23:23 UTCVendor advisory
  19. 2026-06-27 03:08 UTCEPSS rescore
  20. 2026-06-26 20:46 UTCVendor advisory
  21. 2026-06-25 19:35 UTCVendor advisory
  22. 2026-06-25 13:49 UTCEPSS rescore
  23. 2026-06-25 13:49 UTCEPSS rescore
  24. 2026-06-24 14:05 UTCEPSS rescore
  25. 2026-06-23 21:33 UTCEPSS rescore
  26. 2026-06-22 14:25 UTCEPSS rescore
  27. 2026-06-22 14:25 UTCEPSS rescore
  28. 2026-06-21 14:56 UTCEPSS rescore
  29. 2026-06-21 14:56 UTCEPSS rescore
  30. 2026-06-21 01:59 UTCEPSS rescore
  31. 2026-06-19 19:25 UTCEPSS rescore
  32. 2026-06-18 17:52 UTCEPSS rescore
  33. 2026-06-18 17:52 UTCEPSS rescore
  34. 2026-06-17 17:53 UTCEPSS rescore
  35. 2026-06-17 04:20 UTCVendor advisory
  36. 2026-06-16 17:52 UTCEPSS rescore
  37. 2026-06-16 02:52 UTCVendor advisory
  38. 2026-06-15 17:49 UTCEPSS rescore
  39. 2026-06-15 01:02 UTCVendor advisory
  40. 2026-06-13 23:43 UTCVendor advisory
  41. 2026-06-13 23:00 UTCEPSS rescore
  42. 2026-06-12 23:12 UTCEPSS rescore
  43. 2026-06-12 23:12 UTCEPSS rescore
  44. 2026-06-12 19:26 UTCVendor advisory
  45. 2026-06-11 17:59 UTCVendor advisory
  46. 2026-06-11 14:00 UTCEPSS rescore
  47. 2026-06-10 22:18 UTCEPSS rescore
  48. 2026-06-10 16:47 UTCVendor advisory
  49. 2026-06-10 13:22 UTCEPSS rescore
  50. 2026-06-10 13:22 UTCEPSS rescore
  51. 2026-06-09 15:35 UTCVendor advisory
  52. 2026-06-08 14:17 UTCEPSS rescore
  53. 2026-06-08 14:17 UTCEPSS rescore
  54. 2026-06-07 15:25 UTCEPSS rescore
  55. 2026-06-07 15:25 UTCEPSS rescore
  56. 2026-06-06 13:47 UTCEPSS rescore
  57. 2026-06-06 13:47 UTCEPSS rescore
  58. 2026-06-05 22:47 UTCEPSS rescore
  59. 2026-06-04 13:12 UTCEPSS rescore
  60. 2026-06-04 13:12 UTCEPSS rescore
  61. 2026-06-02 20:13 UTCEPSS rescore
  62. 2026-06-01 13:52 UTCEPSS rescore
  63. 2026-06-01 13:52 UTCEPSS rescore
  64. 2026-05-31 22:30 UTCEPSS rescore
  65. 2026-05-31 22:30 UTCEPSS rescore
  66. 2026-05-31 00:16 UTCEPSS rescore
  67. 2026-05-31 00:16 UTCEPSS rescore
  68. 2026-05-29 13:44 UTCEPSS rescore
  69. 2026-05-29 13:44 UTCEPSS rescore
  70. 2026-05-28 13:44 UTCEPSS rescore
  71. 2026-05-28 13:44 UTCEPSS rescore
  72. 2026-05-27 13:40 UTCEPSS rescore
  73. 2026-05-27 13:40 UTCEPSS rescore
  74. 2026-05-26 13:44 UTCEPSS rescore
  75. 2026-05-26 07:18 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 1% probability of exploitation in the next 30 days, which ranks it in the top 54.6% of all scored CVEs.
What is the CVSS score of CVE-2026-42581?
CVE-2026-42581 has a CVSS v3 base score of 9.8 (NVD).
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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