CVE-2026-33871: Netty HTTP/2 CONTINUATION Frame Flood DoS via Zero-Byte Frame Bypass
Noroxi assessment
Priority: Monitor (action score 34/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 1.1% (FIRST EPSS); higher than 66.7% of all records.
- Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
- According to CISA the attack is automatable: targets can be found by mass scanning.
- Fixed version: io.netty:netty-codec-http2 (Maven) 4.2.11.Final, 4.1.132.Final; netty (openSUSE:Leap 15.6) 4.1.132-150200.4.43.1; netty-tcnative (openSUSE:Leap 15.6) 2.0.75-150200.3.36.1.
Low priority for now. Upgrade to io.netty:netty-codec-http2 (Maven) 4.2.11.Final, 4.1.132.Final; netty (openSUSE:Leap 15.6) 4.1.132-150200.4.43.1; netty-tcnative (openSUSE:Leap 15.6) 2.0.75-150200.3.36.1 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
Netty is an asynchronous, event-driven network application framework. In versions prior to 4.1.132.Final and 4.2.10.Final, a remote user can trigger a Denial of Service (DoS) against a Netty HTTP/2 server by sending a flood of `CONTINUATION` frames. The server's lack of a limit on the number of `CONTINUATION` frames, combined with a bypass of existing size-based mitigations using zero-byte frames, allows an user to cause excessive CPU consumption with minimal bandwidth, rendering the server unresponsive. Versions 4.1.132.Final and 4.2.10.Final fix the issue.
- Published
- Mar 27, 2026
- Updated
- Sep 15, 2026
- EPSS
- 1.1% · 66th percentile
- CWE
- CWE-770
Report tools
Action score
34
Monitor
Low priority for now.
- CVSS
- 34 / 40 · 8.7 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 1.1%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · GitHub_M
- 8.7
- NVD has not scored this yet; the score shown is the CNA’s.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| netty | netty | cpe:2.3:a:netty:netty |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- netty nettybefore 4.1.132
- netty netty4.2.0 and later · before 4.2.10
Versions reported by the vendor
Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.
netty netty
- < 4.1.132.Final, >= 4.2.0.Alpha1, < 4.2.10.Finalaffected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | netty | from 0 | — |
| Maven | io.netty:netty-codec-http2 | from 4.2.0.Alpha1 · before 4.2.11.Final | 4.2.11.Final |
| Maven | io.netty:netty-codec-http2 | before 4.1.132.Final | 4.1.132.Final |
| openSUSE:Leap 15.6 | netty | before 4.1.132-150200.4.43.1 | 4.1.132-150200.4.43.1 |
| openSUSE:Leap 15.6 | netty-tcnative | before 2.0.75-150200.3.36.1 | 2.0.75-150200.3.36.1 |
| openSUSE:Tumbleweed | netty | before 4.1.132-1.1 | 4.1.132-1.1 |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-cli | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-commons | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-core-client | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-dto | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-hornetq-protocol | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-hqclient-protocol | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-jakarta-client | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-jakarta-ra | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-jakarta-server | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-jakarta-service-extensions | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-jdbc-store | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-journal | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-selector | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-server | before 0:2.40.0-6.redhat_00012.1.el8eap | 0:2.40.0-6.redhat_00012.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-angus | before 0:2.0.5-1.redhat_00001.1.el8eap | 0:2.0.5-1.redhat_00001.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-angus-activation | before 0:2.0.3-1.redhat_00001.1.el8eap | 0:2.0.3-1.redhat_00001.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-angus-mail | before 0:2.0.5-1.redhat_00001.1.el8eap | 0:2.0.5-1.redhat_00001.1.el8eap |
+96
Same product
netty: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-47691Netty has Insufficient Bailiwick Validation for NS Records40Plan
- CVE-2026-45674Netty Vulnerable to DNS Cache Poisoning via Missing Bailiwick Checks in CNAME Records40Plan
- CVE-2019-20445HttpObjectDecoder.java in Netty before 4.1.44 allows a Content-Length header to be accompanied by a second Content-Length header, or by a Tr40Plan
Published before and after this one in the same product
- ← EarlierCVE-2025-67735Dec 16, 2025 · Netty has a CRLF Injection vulnerability in io.netty.handler.codec.http.HttpRequestEncoder26Monitor
- ← EarlierCVE-2026-33870Mar 27, 2026 · Netty: HTTP Request Smuggling via Chunked Extension Quoted-String Parsing30Monitor
- Later →CVE-2026-41417May 6, 2026 · Netty vulnerable to HTTP request smuggling and RTSP request injection via DefaultHttpRequest.setUri()21Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Maven:io.netty:netty-codec-http2 | 4.1.132.Final | Package registry (OSV) |
| Maven:io.netty:netty-codec-http2 | 4.2.11.Final | Package registry (OSV) |
| opensuse:netty | 4.1.132-150200.4.43.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:netty-tcnative | 2.0.75-150200.3.36.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| red hat:eap8-activemq-artemis | 0:2.40.0-6.redhat_00012.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-activemq-artemis-cli | 0:2.40.0-6.redhat_00012.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-bouncycastle | 0:1.84.0-1.redhat_00001.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-bouncycastle-jmail | 0:1.84.0-1.redhat_00001.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-bouncycastle-pg | 0:1.84.0-1.redhat_00001.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-bouncycastle-pkix | 0:1.84.0-1.redhat_00001.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-bouncycastle-prov | 0:1.84.0-1.redhat_00001.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-bouncycastle-util | 0:1.84.0-1.redhat_00001.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-wildfly | 0:8.1.6-5.GA_redhat_00007.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-wildfly-java-jdk17 | 0:8.1.6-5.GA_redhat_00007.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-wildfly-java-jdk21 | 0:8.1.6-5.GA_redhat_00007.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-wildfly-modules | 0:8.1.6-5.GA_redhat_00007.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| suse:netty | 4.1.132-150200.4.43.1 · SUSE:Linux Enterprise Module for Package Hub 15 SP7 | Package registry (OSV) |
| suse:netty-tcnative | 2.0.75-150200.3.36.1 · SUSE:Linux Enterprise Module for Development Tools 15 SP7 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
No history yet (it accumulates with the daily EPSS job).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2026-100660183 days apartNetty before 4.2.18.Final QpackEncoder Unbounded Memory Retention34Monitor
- CVE-2025-55163226 days apartNetty MadeYouReset HTTP/2 DDoS Vulnerability32Monitor
- CVE-2026-4258247 days apartNetty: HTTP/3 QPACK literal unbounded allocation30Monitor
- CVE-2026-4541677 days apartNetty: SNI handler pre-allocates up to 16 MiB from nine attacker bytes30Monitor
- CVE-2026-4634077 days apartNetty: SCTP reassembly nests buffers without bound30Monitor
- CVE-2026-4874877 days apartNetty HTTP/3 QPACK Blocked Streams Memory Exhaustion30Monitor
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- Integrity
- Availability
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- X
Weakness class (CWE)
CWE-770 · Allocation of Resources Without Limits or ThrottlingCVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- FloodingCAPEC-125likelihood: High · Medium
- Excessive AllocationCAPEC-130likelihood: Medium · Medium
- XML Ping of the DeathCAPEC-147likelihood: Low · Medium
- Exponential Data ExpansionCAPEC-197likelihood: High · Medium
- Serialized Data Parameter BlowupCAPEC-229likelihood: High · High
- Serialized Data with Nested PayloadsCAPEC-230likelihood: Medium · High
- Oversized Serialized Data PayloadsCAPEC-231likelihood: Medium · High
- HTTP DoSCAPEC-469Low
ATT&CK techniques
- Network Denial of Service:Direct Network FloodT1498.001
- Network Denial of Service:Reflection AmplificationT1498.002
- Endpoint Denial of ServiceT1499
- Endpoint Denial of Service: OS Exhaustion FloodT1499.001
- Endpoint Denial of Service:Service Exhaustion FloodT1499.002
- Endpoint Denial of Service:Application Exhaustion FloodT1499.003
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (19 more)Show less
- access.redhat.com/errata/RHSA-2026:10175
- access.redhat.com/errata/RHSA-2026:10184
- access.redhat.com/errata/RHSA-2026:13571
- access.redhat.com/errata/RHSA-2026:14272
- access.redhat.com/errata/RHSA-2026:14276
- access.redhat.com/errata/RHSA-2026:17668
- access.redhat.com/errata/RHSA-2026:17789
- access.redhat.com/errata/RHSA-2026:18054
- access.redhat.com/errata/RHSA-2026:18055
- access.redhat.com/errata/RHSA-2026:18059
- access.redhat.com/errata/RHSA-2026:22619
- access.redhat.com/errata/RHSA-2026:34608
- access.redhat.com/errata/RHSA-2026:65126
- access.redhat.com/errata/RHSA-2026:7109
- access.redhat.com/errata/RHSA-2026:7380
- access.redhat.com/errata/RHSA-2026:8159
- access.redhat.com/errata/RHSA-2026:8509
- access.redhat.com/security/cve/CVE-2026-33871
- bugzilla.redhat.com/show_bug.cgi?id=2452456
Vendor advisories and official records. Exploit/PoC links are deliberately left out.