Off-by-One Write Vulnerability in Envoy Proxy Software
CVE-2026-26309

5.3MEDIUM

Key Information:

Vendor

Envoyproxy

Status
Envoy
Vendor
CVE Published:
10 March 2026

What is CVE-2026-26309?

Envoy, a high-performance edge/middle/service proxy, contains an off-by-one write issue in the method Envoy::JsonEscaper::escapeString() prior to versions 1.37.1, 1.36.5, 1.35.8, and 1.34.13. This flaw can lead to corruption of std::string null-termination, which may result in undefined behavior, including potential application crashes or out-of-bounds reads when the output is treated as a C-string. Users are encouraged to upgrade to the specified patched versions to mitigate these risks.

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Deploy the Patch

Affected Version(s)

envoy >= 1.37.0, < 1.37.1 < 1.37.0, 1.37.1

envoy >= 1.36.0, < 1.36.5 < 1.36.0, 1.36.5

envoy >= 1.35.0, < 1.35.9 < 1.35.0, 1.35.9

References

https://github.com/envoyproxy/envoy/security/advisories/G...
x_refsource_CONFIRM

CVSS V3.1

Score:
5.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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