Advisory details:
ubuntu_osv / UBUNTU-CVE-2026-56821
| Advisory ID | ubuntu_osv/UBUNTU-CVE-2026-56821 |
| Aliases |
CVE-2026-56821
|
| Summary | 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 Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD response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. |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 6.7 |
| Risk | 3.4 |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| There are no known CWE. |
| System | Score | Found at |
|---|---|---|
| cvssv3.1 | 7.4 | https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-56821.json |
| ubuntu-priority | medium | https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-56821.json |
| Reference id | Reference type | URL |
|---|---|---|
| https://github.com/netty/netty/security/advisories/GHSA-g7hg-vrcf-mvmr | ||
| https://ubuntu.com/security/CVE-2026-56821 | ||
| https://www.cve.org/CVERecord?id=CVE-2026-56821 |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
There are no SSVC decisions available.