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CVE-2026-56820— Netty: Missing CertificateID Validation in OCSP Response Allows Replay Attacks

Quick assessment

Affected
netty netty
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Netty是Netty团队开源的一款非阻塞I/O客户端-服务器框架,它主要用于开发Java网络应用程序,如协议服务器和客户端等。 Netty 4.2.0.Final版本至4.2.15.Final版本和4.1.135.Final之前版本存在加密问题漏洞，该漏洞源于OcspClient未验证OCSP响应中的CertificateID是否与请求的CertificateID匹配，可能导致重放攻击，允许绕过另一证书的吊销检查。

CVSS 7.4 · High EPSS 0.31% · P22

Possible ATT&CK Techniques 1 AI

T1553.005 · Mark-of-the-Web Bypass

Affected Version Matrix 2

VendorProduct Version RangeStatus
netty netty >= 4.2.0.Final, < 4.2.16.Final affected
< 4.1.136.Final affected
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I. Basic Information for CVE-2026-56820

Vulnerability Information
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Vulnerability Title
Netty: Missing CertificateID Validation in OCSP Response Allows Replay Attacks
Source: CVE Program / CVE List V5
Vulnerability Description
Netty is a network application framework for development of protocol servers and clients. In versions 4.2.0.Final through 4.2.15.Final and prior to 4.1.135.Final, `OcspClient` does not validate that the `CertificateID` in an OCSP response matches the requested `CertificateID`, which can lead to replay attack. `OcspClient.validateResponse` accepts a legitimately signed `GOOD` status response for an unrelated certificate issued by the same CA, allowing bypass of revocation checks for another certificate. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
证书验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Netty 加密问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Netty是Netty团队开源的一款非阻塞I/O客户端-服务器框架,它主要用于开发Java网络应用程序,如协议服务器和客户端等。 Netty 4.2.0.Final版本至4.2.15.Final版本和4.1.135.Final之前版本存在加密问题漏洞，该漏洞源于OcspClient未验证OCSP响应中的CertificateID是否与请求的CertificateID匹配，可能导致重放攻击，允许绕过另一证书的吊销检查。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
netty netty >= 4.2.0.Final, < 4.2.16.Final -

II. Public POCs for CVE-2026-56820

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 12348 chars
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Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
In-depth vulnerability mechanism
Trigger conditions & impact
Full executable POC code
Exploit chain & mitigation
POC zip download
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III. Intelligence Information for CVE-2026-56820

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Vendor Advisories for CVE-2026-56820 (1)

Vendor Pages for CVE-2026-56820 (2)

Same Patch Batch · netty · 2026-07-21 · 7 CVEs total

CVE-2026-55851 8.7 HIGH Netty codec-haproxy: Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbo
CVE-2026-56819 7.5 HIGH Netty: HTTP/2 decompression leaks ByteBuf reference count when the decompressor channel is
CVE-2026-56816 7.5 HIGH Netty: Memory Exhaustion via HTTP/3 Reserved Frame Types
CVE-2026-56746 6.5 MEDIUM Netty has a Security Control Bypass via CORS Short-Circuit Failure
CVE-2026-56817 Netty: XML External Entity (XXE) injection via unconfigured XML factory when DTD and entit
CVE-2026-56745 Netty SpdyHttpDecoder: ByteBuf Reference Leak on RST_STREAM Leads to Native Memory Exhaust

IV. Related Vulnerabilities

Same product: netty
Same vendor: netty
Same weakness: CWE-295

V. Comments for CVE-2026-56820

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