What’s Vulnerable › Vulnerabilities

CVE-2021-28683

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-05-20 · updated 2026-06-17
• Weakness: CWE-476

Description

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.

Affected products

• envoyproxy envoy: 1.16.2, 1.17.1

References

• https://blog.envoyproxy.io
• https://github.com/envoyproxy/envoy/releases
• https://github.com/envoyproxy/envoy/security/advisories/GHSA-r22g-5f3x-xjgg
• https://github.com/envoyproxy/envoy/security/advisories/GHSA-xw4q-6pj2-5gfg
• https://blog.envoyproxy.io
• https://github.com/envoyproxy/envoy/releases
• https://github.com/envoyproxy/envoy/security/advisories/GHSA-r22g-5f3x-xjgg

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