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CVE Record

CVE-2026-48059: 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.

HighCVSS 8.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This flaw can let a remote, unauthenticated client make affected Netty-based services leak memory when handling certain valid HAProxy PROXY protocol v2 data. Over time, that can exhaust memory and disrupt service availability. The provided sources identify fixed Netty releases, but do not confirm active exploitation.

Executive priority

Treat as a high-priority availability risk for externally reachable Java network services using Netty PROXY protocol handling. Prioritize internet-facing and load-balancer-adjacent services first, then vendor products that embed Netty.

Technical view

The vulnerable HAProxy PROXY protocol v2 codec leaks native or heap memory while parsing nested PP2_TYPE_SSL TLVs at depth two or greater. The parse succeeds, the message proceeds downstream, and normal application release does not free the pinned cumulation ByteBuf. Fixed versions are 4.1.135.Final and 4.2.15.Final.

Likely exposure

Exposure is most likely where applications use affected Netty versions and enable the HAProxy PROXY protocol v2 codec on network-reachable services. Dependency presence alone may not prove exploitability if that codec is unused or untrusted PROXY headers cannot reach the service.

Exploitation context

The CVSS vector describes remote, low-complexity, unauthenticated availability impact. The bundle marks KEV as false, and no provided source confirms exploitation in the wild. The issue is still operationally serious because each triggering connection can leak memory without obvious parse failure.

Researcher notes

The key exposure question is whether PPv2 headers reach Netty's HAProxy codec. The leak occurs on the successful path, so absence of decoder exceptions is not reassuring. Provided sources do not include exploit code, exploitation telemetry, or detailed product-by-product impact beyond Netty and Red Hat advisories.

Mitigation direction

  • Upgrade Netty to 4.1.135.Final or 4.2.15.Final.
  • Apply applicable Red Hat errata for vendor-packaged Netty components.
  • Identify transitive Netty dependencies in Java services and appliances.
  • Check vendor guidance where Netty is bundled by another product.
  • Restart affected services after patching if required by deployment practice.

Validation and detection

  • Confirm deployed Netty versions are not below the fixed releases.
  • Verify whether HAProxy PROXY protocol v2 decoding is enabled.
  • Check whether untrusted clients can reach PROXY v2 listener paths.
  • Review dependency trees for bundled or shaded Netty copies.
  • Monitor memory pressure and direct buffer usage on exposed services.
Prepared
Confidence
high
Sources
11

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-1286: Exact CWE lookup

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cwe · low confidence lookup

CWE-401: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2026-48059 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.7 (4.0)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
13Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.7CVSS 4.0HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N——GitHub_M
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 4.0 score

8.7High
CVSS 4.0 vector shape for CVE-2026-48059Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPnetty-codec-haproxy: Netty HAProxy PROXY protocol v2 codec: Denial of Service via memory leak from crafted PROXY protocol headers
other:Red Hat severity ratingcvssV3_1
  • 2026-06-12T16:02:40.032Z: Reported to Red Hat.
  • 2026-06-12T14:42:44.677Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
nettynetty>= 4.2.0.Final, < 4.2.15.Final, < 4.1.135.FinalListed
Weakness

CWE details

CWE-1286CWE-401

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-1286 · source CWE mapping

Improper Validation of Syntactic Correctness of Input

Improper Validation of Syntactic Correctness of Input represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-401 · source CWE mapping

Missing Release of Memory after Effective Lifetime

Missing Release of Memory after Effective Lifetime represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs