NVD / CVE Program· CNA GitHub_M

CVE-2026-44248: Netty: Resource exhaustion in MqttDecoder

Noroxi assessment

Priority: Monitor (action score 30/100)

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: 0.56% (FIRST EPSS).
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: netty netty 4.2.13.Final.
Severity is disputed: the assigning authority (CNA) scores it 5.3, NVD 7.5.
Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to netty netty 4.2.13.Final 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. Prior to 4.2.13.Final and 4.1.133.Final, the MQTT 5 header Properties section is parsed and buffered before any message size limit is applied. Specifically, in MqttDecoder, the decodeVariableHeader() method is called before the bytesRemainingBeforeVariableHeader > maxBytesInMessage check. The decodeVariableHeader() can call other methods which will call decodeProperties(). Effectively, Netty does not apply any limits to the size of the properties being decoded. Additionally, because MqttDecoder extends ReplayingDecoder, Netty will repeatedly re-parse the enormous Properties sections and buffer the bytes in memory, until the entire thing parses to completion. This can cause high resource usage in both CPU and memory. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

HighCVSS 7.5 · v3.1—No exploit Fix available

Published: May 13, 2026
Updated: Oct 26, 2026
EPSS: 0.5% · 47th percentile
CWE: CWE-400

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 30 / 40 · 7.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.5%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 7.5
CNA · GitHub_M: 5.3; 2.2 point gap

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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.

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Affected 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 4.1.133
netty netty4.2.0 and later · before 4.2.13

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.

io.netty netty-codec-mqtt
- >= 4.2.0.Alpha1, < 4.2.13.Final, < 4.1.133.Finalaffected
netty netty
- >= 4.2.0.Alpha1, < 4.2.13.Final, < 4.1.133.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-mqtt	from 4.2.0.Alpha1 · before 4.2.13.Final	4.2.13.Final
Maven	io.netty:netty-codec-mqtt	before 4.1.133.Final	4.1.133.Final
openSUSE:Tumbleweed	netty	before 4.1.133-1.1	4.1.133-1.1
SUSE:Linux Enterprise Module for Development Tools 15 SP7	netty-tcnative	before 2.0.77-150200.3.39.1	2.0.77-150200.3.39.1
SUSE:Linux Enterprise Module for Package Hub 15 SP7	netty	before 4.1.133-150200.4.46.1	4.1.133-150200.4.46.1

Same product

netty: all records

Other highest-scoring records for the same primary product.

CVE-2026-47691Netty has Insufficient Bailiwick Validation for NS Records
40Plan
CVE-2026-45674Netty Vulnerable to DNS Cache Poisoning via Missing Bailiwick Checks in CNAME Records
40Plan
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 Tr
40Plan

Published before and after this one in the same product

← EarlierCVE-2026-42586May 13, 2026 · Netty: CRLF Injection in Netty Redis Codec Encoder
28Monitor
← EarlierCVE-2026-42587May 13, 2026 · Netty: HttpContentDecompressor maxAllocation bypass via Content-Encoding: br/zstd/snappy enables decompression bomb DoS
30Monitor
Later →CVE-2026-44249Jun 11, 2026 · Netty has an IPv6 Subnet Filter Bypass via Incorrect Comparator Masking
32Monitor

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
netty netty	4.2.13.Final · description	Vendor (CNA)
Maven:io.netty:netty-codec-mqtt	4.1.133.Final	Package registry (OSV)
Maven:io.netty:netty-codec-mqtt	4.2.13.Final	Package registry (OSV)
opensuse:netty	4.1.133-1.1 · openSUSE:Tumbleweed	Package registry (OSV)
suse:netty	4.1.133-150200.4.46.1 · SUSE:Linux Enterprise Module for Package Hub 15 SP7	Package registry (OSV)
suse:netty-tcnative	2.0.77-150200.3.39.1 · 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 researchers

Finders, 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-2026-5585169 days apartNetty codec-haproxy: Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbounded Memory Exhaustion
34Monitor
CVE-2026-5674569 days apartNetty SpdyHttpDecoder: ByteBuf Reference Leak on RST_STREAM Leads to Native Memory Exhaustion
34Monitor
CVE-2026-100661136 days apartNetty HTTP/3 QPACK Prefixed Integer DoS via Unbounded Accumulation
34Monitor
CVE-2026-100662136 days apartNetty HTTP/3 QPACK encoder-stream unbounded memory exhaustion DoS
34Monitor
CVE-2026-425830 days apartNetty: Lz4FrameDecoder resource exhaustion
30Monitor
CVE-2026-425870 days apartNetty: HttpContentDecompressor maxAllocation bypass via Content-Encoding: br/zstd/snappy enables decompression bomb DoS
30Monitor

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).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

TR-26-1140 · Sep 21, 2026(Netty Project Güvenlik Zafiyeti)

All national notices →

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: none
Integrity: none
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: High

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

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)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log

Fix✗ → ✓Sep 28, 2026, 10:48 PM UTC

For records you follow, these changes also arrive as notifications. →

References

github.com/netty/netty/security/advisories/GHSA-jfg9-48mv-9qgx

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records