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Envoy CVE-2026-26309

MEDIUM
Off-by-one Error (CWE-193)
2026-03-10 security-advisories@github.com GHSA-56cj-wgg3-x943
5.3
CVSS 3.1 · GitHub Advisory
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Severity by source

GitHub Advisory PRIMARY
5.3 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

Lifecycle Timeline

3
Analysis Generated
Mar 12, 2026 - 21:55 vuln.today
PoC Detected
Mar 11, 2026 - 16:14 vuln.today
Public exploit code
CVE Published
Mar 10, 2026 - 20:16 nvd
MEDIUM 5.3

DescriptionGitHub Advisory

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.

AnalysisAI

Envoy is a high-performance edge/middle/service proxy. [CVSS 5.3 MEDIUM]

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Vulnerability AssessmentAI

Risk Assessment CVSS 5.3 (MEDIUM). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker could exploit this flaw, crashes or out-of-bounds reads when the resulting string is.
Remediation Fixed in version 1.37.1. … Detailed patch versions, workarounds, and compensating controls in full report.

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Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. …

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CVE-2026-26309 vulnerability details – vuln.today

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