Netty is a network application framework for development of protocol servers and clients. In versions 4.2.0.Final up to (but not including) 4.2.16.Final, and 4.1.0.Final up to (but not including) 4.1.135, the HAProxyMessageDecoder in Netty's codec-haproxy module performs protocol version detection by reading the 13th byte as a signed Java byte and widening it to int without masking; a PROXY protocol v2 binary prefix followed by version byte 0xFF sign-extends to -1, collides with the decoder's need-more-data sentinel, and causes ByteToMessageDecoder to accumulate inbound bytes in an unbounded cumulation buffer until direct memory is exhausted. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.
CVE-2026-55851
“—” beside the score: it is equal to NVD's CVSS score.
This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.6% (49th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.
Also known asEUVD-2026-46438 (ENISA EUVD) · GHSA-q6cq-mhr2-jmr5 (GitHub Security Advisories)Source: ENISA EUVD
- High severity, but no confirmed exploitation yet
A fix is available — apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5HIGHmedium confidence
- EG Risk
- 49EG Risk 49/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity75% × 45%Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation0.6% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability100% × 15%CISA's SSVC Automatable value: yes (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high. - EPSS PROB
- 0.6%
- EPSS %ILE
- 49th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
- EG Likelihood
- 0.6% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-24). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
July 21, 2026
Last Modified
July 30, 2026
Advisory Details (5)
Auto-updated Jul 22, 2026[codec-haproxy] Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbounded Memory Exhaustion · Advisory · netty/netty · GitHub
https://github.com/netty/netty/security/advisories/GHSA-q6cq-mhr2-jmr5netty-4.2.16.Final
Patch available: netty/netty netty-4.2.16.Final
https://github.com/netty/netty/releases/tag/netty-4.2.16.Finalnetty-4.1.136.Final
Patch available: netty/netty netty-4.1.136.Final
https://github.com/netty/netty/releases/tag/netty-4.1.136.Finalcommit bb2ff68a1fb7 (netty/netty)
Patch available: netty/netty netty-4.1.136.Final (contains commit bb2ff68a1fb7)
https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6commit 5b68c61f37aa (netty/netty)
Patch available: netty/netty netty-4.2.16.Final (contains commit 5b68c61f37aa)
https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003bVendor Advisories for CVE-2026-55851(10)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- RHSA-2026:84734Red Hat Product SecurityCritical
Red Hat Security Advisory: RHOAI 3.4.5 - Red Hat OpenShift AI
- RHSA-2026:69296Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat Data Grid 8.6.3 security update
- RHSA-2026:68333Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat build of Cryostat security update
- RHSA-2026:66488Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat AMQ Broker 7.14.1 release and security update
- RHSA-2026:65126Red Hat Product SecurityHigh
Red Hat Security Advisory: RHOAI 2.25.11 - Red Hat OpenShift AI
- RHSA-2026:54622Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat Build of Apache Camel 4.18.3 for Spring Boot release.
- RHSA-2026:48118Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat Build of Apache Camel 4.18.3 for Quarkus 3.33 update is now available (RHBQ 3.33.2.SP3)
- RHSA-2026:47172Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat build of Quarkus 3.33.2.SP3 security update
- +2 more
Patch Availability(7)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| redhat | rhoai/odh-trustyai-service-rhel9:1791792525 | 2026-10-19 | redhat |
| redhat | netty-codec-haproxy | 2026-09-21 | redhat |
| redhat | cryostat/jfr-datasource-rhel9:4.2.0-14 | 2026-09-16 | redhat |
| redhat | rhoai/odh-trustyai-service-rhel9:1788198681 | 2026-09-08 | redhat |
| redhat | patch | 2026-08-05 | redhat |
| redhat | patch | 2026-08-05 | redhat |
| redhat | io.netty/netty-codec-haproxy:4.1.136.Final-redhat-00001 | 2026-07-30 | redhat |
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)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| netty | 1:4.1.48-10 ... 1:4.1.48-9 (16 versions) |
| — |
Debian:12(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| netty | 1:4.1.48-10 ... 1:4.1.48-9 (12 versions) |
| — |
Debian:13(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| netty | 1:4.1.48-10 ... 1:4.1.48-16 (8 versions) |
| — |
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| netty | 1:4.1.48-10 ... 1:4.1.48-16 (7 versions) |
| — |
Maven(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| io.netty:netty-codec-haproxy | 4.1.0.Final ... 4.1.99.Final (136 versions) |
| — |
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 10× in last 7d / 45× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 100 of 236 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 136 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-25 14:18 UTCEG score recompute
- 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-23 23:54 UTCEG score recompute
- 2026-10-23 23:54 UTCVendor advisory
- 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-18 03:29 UTCEG score recompute
- 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-17 03:12 UTCEG score recompute
- 2026-10-17 03:12 UTCVendor advisory
- 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-12 15:55 UTCEG score recompute
- 2026-10-11 19:38 UTCEG score recompute
- 2026-10-11 16:53 UTCEG score recompute
- 2026-10-11 14:16 UTCEG score recompute
Show 75 moreShow fewer
- 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-04 14:46 UTCEG score recompute
- 2026-10-04 14:46 UTCVendor advisory
- 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-01 07:25 UTCEG score recompute
- 2026-10-01 07:25 UTCVendor advisory
- 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-09-28 06:03 UTCEG score recompute
- 2026-09-28 06:03 UTCVendor advisory
- 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.6% · 47th percentile
- 2026-09-24 03:20 UTCEG score recompute
- 2026-09-24 03:20 UTCVendor advisory
- 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.6% · 47th percentile
- 2026-09-23 01:21 UTCEG score recompute
- 2026-09-23 01:21 UTCVendor advisory
- 2026-09-20 05:54 UTCEG score recompute
- 2026-09-20 05:54 UTCVendor advisory
- 2026-09-19 00:19 UTCEG score recompute
- 2026-09-19 00:19 UTCVendor advisory
- 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.6% · 47th percentile
- 2026-09-18 03:46 UTCEG score recompute
- 2026-09-18 03:46 UTCVendor advisory
- 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.6% · 47th percentile
- 2026-09-17 05:04 UTCEG score recompute
- 2026-09-17 05:04 UTCVendor advisory
- 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.6% · 47th percentile
- 2026-09-16 12:34 UTCEG score recompute
- 2026-09-16 12:34 UTCVendor advisory
- 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.6% · 47th percentile
- 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.6% · 47th percentile
- 2026-09-14 04:05 UTCEG score recompute
- 2026-09-14 04:05 UTCVendor advisory
- 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.6% · 47th percentile
- 2026-09-13 15:56 UTCVendor advisory
- 2026-09-13 02:50 UTCEG score recompute
- 2026-09-13 02:50 UTCVendor advisory
- 2026-09-12 09:44 UTCVendor advisory
- 2026-09-11 21:02 UTCEG score recompute
- 2026-09-11 21:02 UTCVendor advisory
- 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.6% · 47th percentile
- 2026-09-11 08:53 UTCEG score recompute
- 2026-09-11 08:53 UTCVendor advisory
- 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.6% · 47th percentile
- 2026-09-09 11:11 UTCEG score recompute
- 2026-09-09 11:11 UTCVendor advisory
- 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.6% · 47th percentile
- 2026-09-07 22:28 UTCEG score recompute
- 2026-09-07 22:28 UTCVendor advisory
- 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.6% · 47th percentile
- 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.6% · 47th percentile
- 2026-09-06 10:39 UTCVendor advisory
- 2026-09-05 20:36 UTCEG score recompute
- 2026-09-05 20:36 UTCVendor advisory
- 2026-09-05 08:25 UTCEG score recompute
- 2026-09-05 08:25 UTCVendor advisory
- 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-09-02 00:55 UTCEG score recompute
- 2026-09-02 00:55 UTCVendor advisory
- 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-08-31 03:26 UTCEG score recompute
Related CVEs(same product + same vendor + same CWE)
Same product
10 shownMaven:io.netty:netty-codec-haproxy · Debian:11:netty
Same vendor
10 shownredhat:RHSA-2026:47172 · redhat:RHSA-2026:50846
Frequently asked(5)
What is CVE-2026-55851?
When was the CVE record for CVE-2026-55851 published?
Is CVE-2026-55851 actively exploited?
What is the CVSS score of CVE-2026-55851?
How do I remediate CVE-2026-55851?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-55851
Is Your Infrastructure Affected by CVE-2026-55851?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.