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NVD / CVE Program· CNA GitHub_M

CVE-2026-50020: Netty's HttpObjectDecoder skips arbitrary initial control characters when only initial CRLF characters are permitted

MediumCVSS 5.3 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 21/100)

  • 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: 0.23% (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: io.netty:netty-codec-http (Maven) 4.2.15.Final, 4.1.135.Final; netty (openSUSE:Tumbleweed) 4.1.135-1.1; netty-tcnative (SUSE:Linux Enterprise Module for Development Tools 15 SP7) 2.0.79-150200.3.45.1.

Low priority for now. Upgrade to io.netty:netty-codec-http (Maven) 4.2.15.Final, 4.1.135.Final; netty (openSUSE:Tumbleweed) 4.1.135-1.1; netty-tcnative (SUSE:Linux Enterprise Module for Development Tools 15 SP7) 2.0.79-150200.3.45.1 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 a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, before reading the first request-line, `HttpObjectDecoder` skips every byte for which `Character.isISOControl(b)` is `true` (0x00–0x1F and 0x7F) as well as all whitespace. RFC 9112 §2.2 only asks servers to ignore empty CRLF lines preceding the request-line — a carefully scoped robustness allowance intended to handle HTTP/1.0 POST workarounds. Silently absorbing NUL bytes, SOH, STX, and other non-CRLF control characters goes significantly beyond this, and can be exploited for request-boundary confusion in pipelined or multiplexed transports where a front-end component treats those bytes differently. Versions 4.1.135.Final and 4.2.15.Final patch the issue.

Published
Jun 12, 2026
Updated
Jun 17, 2026
EPSS
0.2% · 14th percentile

Report tools

JSON

Action score

21

Monitor

Low priority for now.

CVSS
21 / 40 · 5.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
proof of concept
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
5.3
NVD has not scored this yet; the score shown is the CNA’s.

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.

Follow CVE-2026-50020

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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.

VendorProduct
nettynetty

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

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

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12nettyfrom 0—
Mavenio.netty:netty-codec-httpfrom 4.2.0.Final · before 4.2.15.Final4.2.15.Final
Mavenio.netty:netty-codec-httpbefore 4.1.135.Final4.1.135.Final
openSUSE:Tumbleweednettybefore 4.1.135-1.14.1.135-1.1
SUSE:Linux Enterprise Module for Development Tools 15 SP7netty-tcnativebefore 2.0.79-150200.3.45.12.0.79-150200.3.45.1
SUSE:Linux Enterprise Module for Package Hub 15 SP7nettybefore 4.1.135-150200.4.50.14.1.135-150200.4.50.1

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…
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-50010Jun 12, 2026 · Netty's wrapping plain trust manager silently disables hostname verification
    30Monitor
  • ← EarlierCVE-2026-50011Jun 12, 2026 · Netty has unbounded pre-allocation in RedisArrayAggregator from RESP array length
    30Monitor
  • Later →CVE-2026-50560Jun 12, 2026 · Netty susceptible to HTTP/2 Reset Attack with different on-the-wire signature
    27Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Maven:io.netty:netty-codec-http4.1.135.FinalPackage registry (OSV)
Maven:io.netty:netty-codec-http4.2.15.FinalPackage registry (OSV)
opensuse:netty4.1.135-1.1 · openSUSE:TumbleweedPackage registry (OSV)
suse:netty4.1.135-150200.4.50.1 · SUSE:Linux Enterprise Module for Package Hub 15 SP7Package registry (OSV)
suse:netty-tcnative2.0.79-150200.3.45.1 · SUSE:Linux Enterprise Module for Development Tools 15 SP7Package 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.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-4258130 days apartNetty: HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization
    39Monitor
  • CVE-2026-4258430 days apartNetty: HttpClientCodec response desynchronization
    36Monitor
  • CVE-2026-4258530 days apartNetty: HTTP Request Smuggling due to malformed Transfer-Encoding
    30Monitor
  • CVE-2026-3387077 days apartNetty: HTTP Request Smuggling via Chunked Extension Quoted-String Parsing
    30Monitor
  • CVE-2026-5990047 days apartNetty codec-http2: Lack of Host Header Deduplication in HTTP/2→HTTP/1.x Translation Leads to Request Routing Bypass
    27Monitor
  • CVE-2026-8904490 days apartNetty 4.1.133.Final through 4.1.137.Final and 4.2.13.Final through 4.2.17.Final HTTP Request Smuggling via Transfer-Encoding
    27Monitor

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · public bounty program.

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
low · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

CVSS vector

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

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.

ATT&CK techniques

—

References

Show all references (2 more)

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

All records