Netty HAProxy: Unbalanced Reference Count in Nested PP2_TYPE_SSL TLV Parsing Leads to Memory Exhaustion
Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, the HAProxy PROXY protocol v2 codec in netty leaks native or heap memory on every connection when a client sends a syntactically valid header containing nested `PP2_TYPE_SSL` TLVs (type-length-value records) at depth two or greater. The leak occurs on the successful parse path — no exception is thrown, the message fires downstream, the decoder removes itself, and the application releases the `HAProxyMessage` normally. Yet the underlying cumulation buffer (a pooled, potentially direct `ByteBuf` allocated by the channel) remains permanently pinned. Versions 4.1.135.Final and 4.2.15.Final patch the issue.
- Published
- Jun 12, 2026
- Updated
- Sep 18, 2026
- EPSS
- 0.9% · 58th percentile
- CWE
- CWE-401
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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 · 0.9%
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.
Affected systems
| 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 4.1.135
- netty netty4.2.0 and later · before 4.2.15
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
- >= 4.2.0.Final, < 4.2.15.Final, < 4.1.135.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 | all versions | — |
| Maven | io.netty:netty-codec-haproxy | from 4.2.0.Final · before 4.2.15.Final | 4.2.15.Final |
| Maven | io.netty:netty-codec-haproxy | before 4.1.135.Final | 4.1.135.Final |
| openSUSE:Tumbleweed | netty | before 4.1.135-1.1 | 4.1.135-1.1 |
| SUSE:Linux Enterprise Module for Development Tools 15 SP7 | netty-tcnative | before 2.0.79-150200.3.45.1 | 2.0.79-150200.3.45.1 |
| SUSE:Linux Enterprise Module for Package Hub 15 SP7 | netty | before 4.1.135-150200.4.50.1 | 4.1.135-150200.4.50.1 |
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
- CVE-2026-42581Netty: HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization39Monitor
- CVE-2019-20444HttpObjectDecoder.java in Netty before 4.1.44 allows an HTTP header that lacks a colon, which might be interpreted as a separate header with39Monitor
- CVE-2026-75595Netty: SNI Routing Bypass via Fragmented TLS ClientHello Causing Fallback to Default SslContext36Monitor
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-haproxy | 4.1.135.Final | Package registry (OSV) |
| Maven:io.netty:netty-codec-haproxy | 4.2.15.Final | Package registry (OSV) |
| openSUSE:netty | 4.1.135-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| SUSE:netty | 4.1.135-150200.4.50.1 · SUSE:Linux Enterprise Module for Package Hub 15 SP7 | Package registry (OSV) |
| SUSE:netty-tcnative | 2.0.79-150200.3.45.1 · 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.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
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-2026-480060 days apartNetty's Lack of Lifecycle Cleanup Leads to Pooled ByteBuf Leak in RedisArrayAggregator34Monitor
- CVE-2026-5681856 days apartNetty: RedisArrayAggregator max-elements failure leaves retained partial aggregate state26Monitor
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-401 · Missing Release of Memory after Effective LifetimeCVSS 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.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- github.com/netty/netty/releases/tag/netty-4.1.135.Final
- github.com/netty/netty/releases/tag/netty-4.2.15.Final
- github.com/netty/netty/security/advisories/GHSA-h2qv-fj59-j46j
- access.redhat.com/errata/RHSA-2026:26017
- access.redhat.com/errata/RHSA-2026:26018
- access.redhat.com/errata/RHSA-2026:26586
- access.redhat.com/errata/RHSA-2026:34608
- access.redhat.com/errata/RHSA-2026:36820
- access.redhat.com/errata/RHSA-2026:37390
- access.redhat.com/errata/RHSA-2026:41951
- access.redhat.com/errata/RHSA-2026:48151
- access.redhat.com/errata/RHSA-2026:50085
- access.redhat.com/errata/RHSA-2026:53644
- access.redhat.com/errata/RHSA-2026:53645
- access.redhat.com/errata/RHSA-2026:53646
- access.redhat.com/errata/RHSA-2026:54435
- access.redhat.com/errata/RHSA-2026:65126
- access.redhat.com/errata/RHSA-2026:66488
- access.redhat.com/security/cve/CVE-2026-48059
- bugzilla.redhat.com/show_bug.cgi?id=2488437
Vendor advisories and official records. Exploit/PoC links are deliberately left out.