CVE-2021-28683

Red Hat Security Advisory: Red Hat OpenShift Service Mesh 1.1.13 security update

7.5 HighFix available

An issue was discovered in Envoy through 1.71.1. There is a remotely exploitable NULL pointer dereference and crash in TLS when an unknown TLS alert code is received.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: High

Exploit likelihood

1.69%Up 0.9 points since May 21, 2021

What each source reports

NVD Score used 7.5

An issue was discovered in Envoy through 1.71.1. There is a remotely exploitable NULL pointer dereference and crash in TLS when an unknown TLS alert code is received.

Record: CVE-2021-28683
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0: 5.0 MediumAV:N/AC:L/Au:N/C:N/I:N/A:P
Weakness: CWE-476
Updated: 2026-11-02

CVE List No score

An issue was discovered in Envoy through 1.71.1. There is a remotely exploitable NULL pointer dereference and crash in TLS when an unknown TLS alert code is received.

Record: CVE-2021-28683
Updated: 2026-11-02

EUVDEUVD-2021-15340 No score

An issue was discovered in Envoy through 1.71.1. There is a remotely exploitable NULL pointer dereference and crash in TLS when an unknown TLS alert code is received.

Record: EUVD-2021-15340
Updated: 2026-11-03

OSV 7.5

An issue was discovered in Envoy through 1.71.1. There is a remotely exploitable NULL pointer dereference and crash in TLS when an unknown TLS alert code is received.

Record: CVE-2021-28683
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVRHSA-2021:1322 7.5

Red Hat Security Advisory: Red Hat OpenShift Service Mesh 1.1.13 security update

Record: RHSA-2021:1322
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVRHSA-2021:1324 7.5

Red Hat Security Advisory: Red Hat OpenShift Service Mesh 2.0.3 security update

Record: RHSA-2021:1324
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVBIT-envoy-2021-28683 No score

An issue was discovered in Envoy through 1.71.1. There is a remotely exploitable NULL pointer dereference and crash in TLS when an unknown TLS alert code is received.

Record: BIT-envoy-2021-28683
Updated: 2026-11-02

Affected products

envoyproxy envoy

Affected packages

Affected packages
Package	Affected	Fixed
`envoy` Bitnami	1.16.2 up to 1.16.3, 1.17.1 up to 1.17.2	1.16.31.17.2
`servicemesh-pilot-agent` Red Hat:service_mesh:1.1::el8 From an advisory covering 4 CVEs	before 0:1.1.13-3.el8	0:1.1.13-3.el8
`servicemesh-pilot-discovery` Red Hat:service_mesh:1.1::el8 From an advisory covering 4 CVEs	before 0:1.1.13-3.el8	0:1.1.13-3.el8
`servicemesh-proxy` Red Hat:service_mesh:1.1::el8 From an advisory covering 4 CVEs	before 0:1.1.13-1.el8	0:1.1.13-1.el8
`servicemesh-proxy` Red Hat:service_mesh:2.0::el8 From an advisory covering 3 CVEs	before 0:2.0.3-1.el8	0:2.0.3-1.el8

History

History
Recorded	Changed	Sources
Nov 6, 2026	affected, facts
Nov 3, 2026	aliases	EUVD
Nov 2, 2026	first indexed	CVE List, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-28683 is a high vulnerability (CVSS 7.5) in Envoyproxy Envoy, published May 20, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.69%, the 77th percentile. Fixed in envoy 1.16.3.

References

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