Netty: TOCTOU in OcspServerCertificateValidator

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.4 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

• CVE-2026-56822: 0.17% estimated exploitation activity in the next 30 days; percentile 6.81 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Netty's 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. Details In 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…

Published by the source

22 Jul 2026, 21:47 UTC

Last modified by the source

22 Jul 2026, 21:47 UTC

Source last checked

26 Oct 2026, 16:54 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-wc96-39fc-566f

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# Patch Next advisory brief: CVE-2026-56822

Advisory: Netty: TOCTOU in OcspServerCertificateValidator
IDs: CVE-2026-56822, GHSA-wc96-39fc-566f
Record: https://patchnext.com/advisories/cve-2026-56822 (revision 1, source checked 26 Oct 2026, 16:54 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: io.netty:netty-handler-ssl-ocsp 4.2.16.Final, 4.1.136.Final. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven io.netty:netty-handler-ssl-ocsp: affected >= 4.2.0.Final, < 4.2.16.Final; < 4.1.136.Final; fixed in 4.2.16.Final, 4.1.136.Final

## Suggested inspection (read-only)
- Maven io.netty:netty-handler-ssl-ocsp: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on io.netty:netty-handler-ssl-ocsp.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-wc96-39fc-566f (GitHub-reviewed advisory GHSA-wc96-39fc-566f lists affected ranges: Maven io.netty:netty-handler-ssl-ocsp >=4.2.0.Final =0 <4.1.136.Final)

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