Is CVE-2025-64763 in the CISA KEV catalog?

No. CVE-2025-64763 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2025-64763?

CVE-2025-64763 has a CVSS v3 base score of 3.7 (LOW).

What is the EPSS score for CVE-2025-64763?

CVE-2025-64763 has an EPSS score of 0.28% (20th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2025-64763?

Upgrade envoy to 1.36.3 or later.

CVE & CISA-KEV Catalog

CVE-2025-64763

LOW

3.7

CVSS v3

NVD

Description

Envoy is a high-performance edge/middle/service proxy. In 1.33.12, 1.34.10, 1.35.6, 1.36.2, and earlier, when Envoy is configured in TCP proxy mode to handle CONNECT requests, it accepts client data before issuing a 2xx response and forwards that data to the upstream TCP connection. If a forwarding proxy upstream from Envoy then responds with a non-2xx status, this can cause a de-synchronized CONNECT tunnel state. By default Envoy continues to allow early CONNECT data to avoid disrupting existing deployments. The envoy.reloadable_features.reject_early_connect_data runtime flag can be set to reject CONNECT requests that send data before a 2xx response when intermediaries upstream from Envoy may reject establishment of a CONNECT tunnel.

CWE-693Protection Mechanism Failure

How to fix

Remediation Available

envoyNVD

Affected:>= 1.36.0, < 1.36.3Fixed in:1.36.3CVE-2025-64763derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityNone

AvailabilityNone

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

Exploit Intelligence

0.28%probability of exploitation in 30 days

20thpercentile

Low risk: more likely to be exploited than 20% of all known CVEs.

References

Patch1

github.com

Related Vulnerabilities

Other CWE-693 (Protection Mechanism Failure) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2013-2465	Critical	9.8	99%	KEV + Ransom	-
CVE-2024-21412	High	8.1	95%	KEV + Ransom	Fix
CVE-2013-0431	Medium	5.3	90%	KEV + Ransom	-
CVE-2025-40536	High	8.1	82%	KEV	Fix
CVE-2019-1003030	Critical	9.9	76%	KEV	-
CVE-2025-0411	High	7.0	67%	KEV	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-12-05.