What’s Vulnerable › Vulnerabilities
CVE-2026-26309: Envoy has an off-by-one write in JsonEscaper::escapeString()
- Severity: medium (CVSS 5.3 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.4% probability of exploitation in the next 30 days
- Public exploit or detection template: yes
- Published: 2026-03-10 · updated 2026-06-17
- Weakness: CWE-193
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.
Affected products
- envoyproxy envoy: before 1.34.13; from 1.35.0 before 1.35.8; from 1.36.0 before 1.36.5; 1.37.0 — fixed in 1.34.13, 1.35.8, 1.36.5
How to fix
Upgrade to a fixed version: envoyproxy envoy 1.34.13, 1.35.8, 1.36.5. Check the vendor advisory for mitigations.
References
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