# CVE-2026-56822: Netty: TOCTOU in OcspServerCertificateValidator > Attackers can exploit a race condition in Netty's OCSP validator to leak sensitive data to revoked servers before the connection is closed. - **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 28 Jul 2026 - **Updated:** 30 Jul 2026 - **Also known as:** CLEANSTART-2026-DF40874, CLEANSTART-2026-RU96271, DEBIAN-CVE-2026-56822, ECHO-b0f9-ed1f-4fd2, GHSA-wc96-39fc-566f, MINI-4jfh-3j3g-9gqj, MINI-4mxq-6cxx-f48g, MINI-6g5g-v55r-g975, MINI-7m58-3585-8hc5, MINI-8xrx-f8r8-22gv, MINI-qjg3-8xj5-w263, MINI-rxgx-x2w2-w52x, MINI-w363-8m3c-882m, MINI-w799-vw4f-f482, MINI-xqrr-q2mh-r2fq, UBUNTU-CVE-2026-56822 ## What is CVE-2026-56822? CVE-2026-56822 is a high-severity vulnerability in Netty Netty, published on 28 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official 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. Weakness: CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition) ## Which versions are affected by CVE-2026-56822? 4 open source packages ship an affected version, including io.netty:netty-handler-ssl-ocsp. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `io.netty:netty-handler-ssl-ocsp` | Maven | All versions | 4.1.136.Final | | `io.netty:netty-handler-ssl-ocsp` | Maven | All versions | 4.1.136.Final | | `io.netty:netty-handler-ssl-ocsp` | Maven | From 4.2.0.Final | 4.2.16.Final | | `io.netty:netty-handler-ssl-ocsp` | Maven | From 4.2.0.Final | 4.2.16.Final | Products: Netty Netty. ## How do I fix CVE-2026-56822? Upgrade io.netty:netty-handler-ssl-ocsp to a fixed version for your release line: 4.1.136.Final or 4.2.16.Final. ## Is CVE-2026-56822 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-56822 exists. ## Other vulnerabilities in Netty Netty - [CVE-2026-75595](https://insights.sbomify.com/CVE-2026-75595/): Netty: SNI Routing Bypass via Fragmented TLS ClientHello Causing Fallback to Default SslContext (critical 9.1) - [CVE-2026-75596](https://insights.sbomify.com/CVE-2026-75596/): Netty: Fragmented ClientHello records trigger quadratic pre-handshake reassembly in default SNI parsing (high 8.7) - [CVE-2026-59901](https://insights.sbomify.com/CVE-2026-59901/): Netty Bzip2Decoder: Infinite Loop in RLE State Machine Leads to Event-Loop Thread Hang (high 8.7) - [CVE-2026-55851](https://insights.sbomify.com/CVE-2026-55851/): Netty codec-haproxy: Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbounded Memory Exhaustion (high 8.7) - [CVE-2026-56745](https://insights.sbomify.com/CVE-2026-56745/): Netty SpdyHttpDecoder: ByteBuf Reference Leak on RST_STREAM Leads to Native Memory Exhaustion (high 8.7) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-56822 and fix it if it is affected. What it is: CVE-2026-56822 is a high-severity vulnerability in Netty Netty, published on 28 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-56822 exists. Affected packages and fixed versions: - io.netty:netty-handler-ssl-ocsp (Maven): affected all versions; fixed in 4.1.136.Final - io.netty:netty-handler-ssl-ocsp (Maven): affected all versions; fixed in 4.1.136.Final - io.netty:netty-handler-ssl-ocsp (Maven): affected from 4.2.0.Final; fixed in 4.2.16.Final - io.netty:netty-handler-ssl-ocsp (Maven): affected from 4.2.0.Final; fixed in 4.2.16.Final Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-56822/ (Markdown: https://insights.sbomify.com/CVE-2026-56822/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-56822 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-56822 - OSV: https://osv.dev/vulnerability/CVE-2026-56822 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-56822/ Summaries are generated and may contain mistakes; the official description above is the record.