CVE-2026-47778
MEDIUMDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
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
Impact
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 7% of all known CVEs.
References
Related Vulnerabilities
Other CWE-158 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-47812 | Critical | 10.0 | 95% | KEV | Fix |
| CVE-2009-1537 | High | 8.8 | 51% | KEV | - |
| CVE-2022-20812 | Critical | 9.0 | 1.8% | - | Fix |
| CVE-2020-14500 | Critical | 10.0 | 1.7% | - | - |
| CVE-2020-7928 | Medium | 6.5 | 1.4% | - | Fix |
| CVE-2022-20813 | Critical | 9.0 | 1.1% | - | Fix |
Common questions
How do I fix CVE-2026-47778?
Upgrade envoy to 1.38.3 or later.
Is CVE-2026-47778 being actively exploited?
Not that we know of. CVE-2026-47778 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.18% is the estimated probability that it will be exploited in the next 30 days. That is higher than 7% of all scored CVEs.
How severe is CVE-2026-47778?
CVE-2026-47778 has a CVSS v3 base score of 4.4, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-47778 affect?
Published advisories record a fix for envoy (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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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 2026-06-29.