CVE-2026-26309
Received Received - Intake
Off-by-One Write in Envoy JsonEscaper Causes Crashes

Publication date: 2026-03-10

Last updated on: 2026-03-11

Assigner: GitHub, Inc.

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 Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2026-03-10
Last Modified
2026-03-11
Generated
2026-06-16
AI Q&A
2026-03-10
EPSS Evaluated
2026-06-15
NVD
CVE-2026-26309
EUVD
EUVD-2026-10800
Affected Vendors & Products
Showing 4 associated CPEs
Vendor Product Version / Range
envoyproxy envoy to 1.34.13 (exc)
envoyproxy envoy From 1.35.0 (inc) to 1.35.8 (exc)
envoyproxy envoy From 1.36.0 (inc) to 1.36.5 (exc)
envoyproxy envoy 1.37.0
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-193 A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.
Attack-Flow Graph
AI Quick Actions
Instant insights powered by AI
Executive Summary

This vulnerability is an off-by-one write error in the Envoy proxy's JsonEscaper::escapeString() function. It can corrupt the null-termination of a std::string, which may cause undefined behavior. Specifically, when the corrupted string is later used as a C-string, it can lead to crashes or out-of-bounds reads.

Impact Analysis

The vulnerability can cause the Envoy proxy to crash or behave unpredictably due to out-of-bounds reads. This can lead to denial of service or instability in systems relying on Envoy for edge, middle, or service proxy functions.

Compliance Impact

I don't know

Detection Guidance

I don't know

Mitigation Strategies

To mitigate this vulnerability, you should upgrade Envoy to one of the fixed versions: 1.37.1, 1.36.5, 1.35.8, or 1.34.13.

Chat Assistant
Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-26309. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70
EPSS Chart