CVE-2026-26309
Envoy has an off-by-one write in JsonEscaper::escapeString()
5.3
MEDIUM
CVSS 3.1
EPSS 0.00%
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.
How to fix CVE-2026-26309
To remediate CVE-2026-26309, upgrade the affected package to a fixed version below.
- —upgrade to 1.34.13 or later
- —no fix listed
Is CVE-2026-26309 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- from 0, < 1.34.13, >= 1.35.0, < 1.35.9, >= 1.36.0, < 1.36.5, >= 1.37.0, < 1.37.1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |