CVE-2026-26309

Envoy has an off-by-one write in JsonEscaper::escapeString()

State: Published
Severity: 5.3 Medium
Published: Mar 10, 2026
Updated: Mar 10, 2026
Reserved: Feb 13, 2026

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.

Scores

CVSS	Score	Vector	Source
3.1	5.3 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L	GitHub_M

Weaknesses

CWE-193 Off-by-one Error

Affected Products

Product	Versions
envoyenvoyproxy	>= 1.37.0, < 1.37.1Affected >= 1.36.0, < 1.36.5Affected >= 1.35.0, < 1.35.9Affected < 1.34.13Affected

References

https://github.com/envoyproxy/envoy/security/advisories/GHSA-56cj-wgg3-x943

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