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CVE-2026-56822— Netty: TOCTOU in OcspServerCertificateValidator

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 4.1.136.Final之前版本和4.2.16.Final之前版本存在竞争条件问题漏洞，该漏洞源于OcspServerCertificateValidator在异步OCSP验证完成前转发SslHandshakeCompletionEvent，存在竞争条件问题，可能导致客户端敏感数据泄露。

CVSS 7.4 · High EPSS 0.17% · P6

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

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-2026-56822

Vulnerability Information
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Vulnerability Title
Netty: TOCTOU in OcspServerCertificateValidator
Source: CVE Program / CVE List V5
Vulnerability Description
Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator forwards the SslHandshakeCompletionEvent before the asynchronous OCSP validation completes. This allows the client's downstream handlers to send sensitive application data (e.g., HTTP requests) to a revoked server before the channel is closed by the OCSP check. n io.netty.handler.ssl.ocsp.OcspServerCertificateValidator#userEventTriggered, when an SslHandshakeCompletionEvent is received, the validator immediately calls ctx.fireUserEventTriggered(evt). It then initiates an asynchronous OCSP query using OcspClient.query. Because the handshake completion event is forwarded immediately, downstream handlers in the client's pipeline are notified that the TLS handshake is successful. They may then begin reading and processing incoming application data or sending outgoing data. If the OCSP response later indicates the server's certificate is REVOKED, the validator closes the channel, but by this time, the client may have already leaked sensitive data to a revoked server or processed malicious responses from it. This issue has been 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
检查时间与使用时间(TOCTOU)的竞争条件
Source: CVE Program / CVE List V5
Vulnerability Title
Netty 竞争条件问题漏洞
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 4.1.136.Final之前版本和4.2.16.Final之前版本存在竞争条件问题漏洞，该漏洞源于OcspServerCertificateValidator在异步OCSP验证完成前转发SslHandshakeCompletionEvent，存在竞争条件问题，可能导致客户端敏感数据泄露。
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-2026-56822

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 15576 chars
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III. Intelligence Information for CVE-2026-56822

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Vendor Advisories for CVE-2026-56822 (1)

Same Patch Batch · netty · 2026-07-28 · 3 CVEs total

CVE-2026-56821 7.4 HIGH Netty: Out-of-date OCSP Responses Accepted by OcspServerCertificateValidator
CVE-2026-59921 5.7 MEDIUM Netty: CRLF Injection via Multipart Filename in Netty HttpPostRequestEncoder

IV. Related Vulnerabilities

Same product: netty
Same vendor: netty
Same weakness: CWE-367

V. Comments for CVE-2026-56822

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