CVE-2026-26309 — Off-by-one Error in Envoy

CWE-193 — Off-by-one Error8 documents4 sources
Severity
5.3MEDIUMNVD
EPSS
0.0%
top 99.90%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
2
Envoyproxy EnvoyGithub.com Envoyproxy Envoy
Timeline
PublishedMar 10

Description

Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, an off-by-one write in Envoy::JsonEscaper::escapeString() can corrupt std::string null-termination, causing undefined behavior and potentially leading to crashes or out-of-bounds reads when the resulting string is later treated as a C-string. This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:LExploitability: 3.9 | Impact: 1.4

Affected Packages3 packages

▶NVDenvoyproxy/envoy1.35.0 — 1.35.8+3
▶Gogithub.com/envoyproxy_envoy1.36.0 — 1.36.4+2
▶CVEListV5envoyproxy/envoy>= 1.35.0, < 1.35.9, >= 1.36.0, < 1.36.5, >= 1.37.0, < 1.37.1+2

🔴Vulnerability Details

2
GHSA
Envoy affected by off-by-one write in JsonEscaper::escapeString()↗2026-03-10
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OSV
Envoy affected by off-by-one write in JsonEscaper::escapeString()↗2026-03-10
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🕵️Threat Intelligence

5
Wiz
CVE-2026-26308 Impact, Exploitability, and Mitigation Steps | Wiz↗
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Wiz
CVE-2026-26310 Impact, Exploitability, and Mitigation Steps | Wiz↗
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Wiz
CVE-2026-26311 Impact, Exploitability, and Mitigation Steps | Wiz↗
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Wiz
CVE-2026-26309 Impact, Exploitability, and Mitigation Steps | Wiz↗
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Wiz
CVE-2026-26330 Impact, Exploitability, and Mitigation Steps | Wiz↗
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