TI-2026-35272 Aliases CVE-2026-47778

Envoy: Embedded NUL in TLS DNS SAN Truncation in the Default TLS Certificate Validator. (Auth Bypass)

MEDIUM 54CWE-158Published 2026-06-26 · Updated 2026-06-27

Key facts

Attack vector: Network
Privileges required: High
User interaction: None
Attack complexity: High
Impact type: —
Confidentiality · integrity · availability: High · None · None
Fix status: Partial Red Hat: 2 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.

Summary

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a structural flaw was identified in DefaultCertValidator::verifySubjectAltName where the extracted DNS SAN string is cast to a C-style string using .c_str() before being passed to the Utility::dnsNameMatch() algorithm. If the attacker serves a certificate with a dNSName SAN containing an embedded NUL byte, the helper Utility::generalNameAsString captures the complete string including the NUL. However, when .c_str() evaluates it, implicit conversion to absl::string_view inside dnsNameMatch relies on strlen(), prematurely truncating the evaluation context. Envoy evaluates trucated string against the exact required config_san match and returns true, thereby successfully validating the string with the Nul byte for an upstream routing. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00212 11th percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by NVD

Fix Partial envoy (envoyproxy): 1.38.1, 1.37.3, 1.36.7 +1Red Hat: 2 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
envoyproxy	envoy	1.38.0 to before 1.38.1; 1.37.0 to before 1.37.3; 1.36.0 to before 1.36.7; before 1.35.11	1.38.1, 1.37.3, 1.36.7, 1.35.11	Patch available	CNA

envoy Vendorenvoyproxy Affected 1.38.0 to before 1.38.1; 1.37.0 to before 1.37.3; 1.36.0 to before 1.36.7; before 1.35.11 Fixed in 1.38.1, 1.37.3, 1.36.7, 1.35.11 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:envoyproxy:envoy::::::::	before 1.35.13; 1.36.0 to before 1.36.9; 1.37.0 to before 1.37.5; 1.38.0 to before 1.38.3	Vulnerable	envoyproxy

cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* Versions before 1.35.13; 1.36.0 to before 1.36.9; 1.37.0 to before 1.37.5; 1.38.0 to before 1.38.3 Vulnerable ·envoyproxy

Remediation

Fix · CNA envoy (envoyproxy) Fixed in 1.38.1, 1.37.3, 1.36.7, 1.35.11

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Product	Status	Plan or fix
OpenShift Service Mesh 2	Affected	No fix yet: Fix deferred
OpenShift Service Mesh 3	Affected	No fix yet: Fix deferred

Timeline

2026-10-02 Threatist record created from CVE-2026-47778

References

Exploit 1

https://github.com/envoyproxy/envoy/security/advisories/GHSA-f8x4-rw5x-f3r7

TI-2026-79288 Out-of-bounds write in Google Brotli decoder KEVCVSS 4.0CRITICAL 9.2
TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
TI-2024-20001 HTTP/2: CPU exhaustion due to CONTINUATION frame flood CVSS 3.1HIGH 7.5
TI-2024-18524 HTTP/2: memory exhaustion due to CONTINUATION frame flood CVSS 3.1HIGH 7.5
TI-2023-12215 Envoy client may fake the header `x-envoy-original-path` CVSS 3.1CRITICAL 9.1
TI-2023-18002 Envoy vulnerable to OAuth2 credentials exploit with permanent validity CVSS 3.1CRITICAL 9.8

See all 126 →

Sources

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