CVE•Published 2026-07-29•Modified 2026-08-07•0 articles on news•5 live references•NVD data

CVE-2026-56821Netty · Netty

Vulnerability data via NVD (ingested)

CVSS v3.1

7.4

HIGH

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

EPSS percentile

Exploit Prediction Scoring System · top 96% of all CVEs

Weaknesses (CWE)

CWE-299Improper Check for Certificate Revocation

Description

Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD response to bypass revocation of a since-revoked certificate. Exploitation can lead to certificate revocation bypass via replay of an expired OCSP response. Any application using OcspServerCertificateValidator is affected; a revoked certificate can be accepted. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.

Timeline

Published 2026-07-29

Modified 2026-08-07

External references

NVD MITRE Exploit-DB trickest/cve VulnCheck

Search for exposed instances

Shodan + Censys queries derived from NVD's CPE data. The vuln tag catches assets Shodan has explicitly linked to this CVE; the product / banner fingerprints find exposed instances even when the vuln tag was never applied (which is common).

Shodan · vuln tag0 hosts

vuln:CVE-2026-56821

Hosts Shodan has explicitly fingerprinted as vulnerable.

Shodan · product

product:"Netty Netty"

All exposed Netty Netty instances — cross-reference with the CVE's affected-version range.

Shodan · banner/body mention

http.html:"Netty"

HTTP body or banner mentions "Netty" — catches deploys Shodan didn't identify as a product.

More intel sources (5)

Shodan report

vuln:CVE-2026-56821