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CVE Record

CVE-2026-33870: Netty: HTTP Request Smuggling via Chunked Extension Quoted-String Parsing

Netty is an asynchronous, event-driven network application framework. In versions prior to 4.1.132.Final and 4.2.10.Final, Netty incorrectly parses quoted strings in HTTP/1.1 chunked transfer encoding extension values, enabling request smuggling attacks. Versions 4.1.132.Final and 4.2.10.Final fix the issue.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Netty had a parsing bug in HTTP chunked request handling. An attacker could exploit disagreement between components that read the same HTTP request, potentially making a backend process a hidden or altered request. This mainly threatens application integrity where vulnerable Netty-based services handle HTTP/1.1 traffic.

Executive priority

Treat as high priority for externally reachable Java services and platforms using Netty. The business risk is request integrity, not data disclosure, but request smuggling can undermine routing, authorization, or application assumptions.

Technical view

Before 4.1.132.Final and 4.2.10.Final, Netty incorrectly parsed quoted strings in HTTP/1.1 chunked transfer encoding extension values. The issue is classified as CWE-444 request smuggling and has CVSS 7.5, network reachable, low complexity, no authentication, and high integrity impact.

Likely exposure

Exposure is most likely in services using vulnerable Netty versions for HTTP/1.1 request handling, especially behind proxies, gateways, or load balancers. Red Hat advisories indicate downstream packaged exposure should also be checked where Red Hat-supported components include Netty.

Exploitation context

The bundle does not show CISA KEV listing or confirmed active exploitation. Public references discuss the parsing class, but this assessment should not assume exploitation in the wild without additional evidence.

Researcher notes

Focus validation on parser differentials between front-end intermediaries and vulnerable Netty backends. Avoid assuming product impact beyond Netty and named vendor advisories. Evidence is sufficient for affected versions and fixed releases, but incomplete for real-world exploitation.

Mitigation direction

  • Upgrade Netty to 4.1.132.Final, 4.2.10.Final, or later supported releases.
  • Apply applicable Red Hat security advisories for Red Hat-packaged affected components.
  • Prioritize internet-facing services and proxy-to-backend HTTP/1.1 paths.
  • If immediate upgrade is blocked, check vendor guidance for supported interim controls.

Validation and detection

  • Inventory applications and images for Netty versions before 4.1.132.Final or 4.2.10.Final.
  • Map vulnerable services that receive HTTP/1.1 traffic through intermediaries.
  • Confirm deployed packages include the fixed Netty version or relevant Red Hat errata.
  • Review gateway and backend logs for unexplained request routing or malformed chunked traffic.
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-444: 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.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-33870 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
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A: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
24Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: 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
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N3.93.6GitHub_M
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-33870Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
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-SADPio.netty/netty-codec-http: Netty: Request smuggling via incorrect parsing of HTTP/1.1 chunked transfer encoding extension values
other:Red Hat severity ratingcvssV3_1
  • 2026-03-27T21:01:59.865Z: Reported to Red Hat.
  • 2026-03-27T19:54:15.586Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
nettynetty< 4.1.132.Final, >= 4.2.0.Alpha1, < 4.2.10.FinalListed
Weakness

CWE details

CWE-444

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

CWE-444 · source CWE mapping

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs