Cyber Resilience

CVE-2026-42586

Netty ≤ 4.1.133

Public PoC
Published
13 May 2026
Modified
17 June 2026
Patch / advisory
View advisory
CVSS Score v3.1 6.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
EPSS Score 0.0020 10th percentile
Risk Priority 50 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-42586 is a medium-severity CRLF Injection (CWE-93) vulnerability in Netty Netty. Its CVSS base score is 6.8 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Content Injection (T1659); ranked at the 10th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A05:2025 Injection

EU & UK References

Vulnerability Data

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, the Netty Redis codec encoder (RedisEncoder) writes user-controlled string content directly to the network output buffer without validating or sanitizing CRLF (\r\n) characters. Since the Redis Serialization…

more

Protocol (RESP) uses CRLF as the command/response delimiter, an attacker who can control the content of a Redis message can inject arbitrary Redis commands or forge fake responses. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

CWE(s)
CWE-93

Related Threats

MITRE ATT&CK Enterprise Techniques

T1659 Content Injection Initial Access
Adversaries may gain access and continuously communicate with victims by injecting malicious content into systems through online network traffic.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-67735Same product: Netty Netty
CVE-2026-41417Same product: Netty Netty
CVE-2026-42578Same product: Netty Netty
CVE-2026-42584Same product: Netty Netty
CVE-2026-42581Same product: Netty Netty
CVE-2026-33870Same product: Netty Netty
CVE-2026-50020Same product: Netty Netty
CVE-2026-42585Same product: Netty Netty
CVE-2025-58056Same product: Netty Netty
CVE-2026-48059Same product: Netty Netty

Affected Assets

netty
netty
≤ 4.1.133 · 4.2.0 — 4.2.13

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V4.2.4

Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation good match

Input validation directly stops untrusted data containing CRLF sequences from reaching the component that treats CRLF as a delimiter.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly require input neutralization and validation to block CRLF injection.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect CRLF flaws but does not itself implement the neutralization.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle mandates input validation and output encoding that directly prevents CRLF injection.

A.8.26 Application security requirements partial match
prevents

Application security requirements include rules for neutralizing special characters such as CRLF in inputs.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles encourage safe handling of untrusted data but do not prescribe specific CRLF controls.

A.8.28 Secure coding partial match
prevents

Secure coding standards explicitly require neutralization of CRLF sequences, fully addressing this weakness.

References