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Medium

Envoy has an off-by-one write in JsonEscaper::escapeString()

Type: advisorySources: OSV

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.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-26309
Confirmed fixed CVEs
Not specified
Updated in this feed
7 Nov 2026, 05:05 UTC · Revision 1

Source evidence

Envoy has an off-by-one write in JsonEscaper::escapeString()

core-osv · Original source

Published 10 Mar 2026, 19:04 UTC

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.

osv:CVE-2026-26309
Complete source record
{
  "id": "10c4d263fc67d57acc3dd1fdc35376333a0991f88d0497228efc2a61daa2d757",
  "url": "https://osv.dev/vulnerability/CVE-2026-26309",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Envoy has an off-by-one write in JsonEscaper::escapeString()",
    "summary": "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.",
    "evidence": "osv:CVE-2026-26309",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-26309",
      "aliases": [
        "BIT-envoy-2026-26309",
        "CVE-2026-26309",
        "GHSA-56cj-wgg3-x943"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/envoyproxy/envoy",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "7c0fda3dc457de6ee4585e8129e3f5728d65f367"
                },
                {
                  "introduced": "84305a6cb64bd55aaf606bdd53de7cd6080427a1"
                },
                {
                  "fixed": "9a0cdcadabcb7baa2348afa1178e083f8d0fe2d7"
                },
                {
                  "introduced": "63ee0dc79dce88117c6bd2df5a742f8eb67ea980"
                },
                {
                  "fixed": "41749943780b54b70b510b1b1a4805ae529e174a"
                },
                {
                  "introduced": "6d9bb7d9a85d616b220d1f8fe67b61f82bbdb8d3"
                },
                {
                  "last_affected": "6d9bb7d9a85d616b220d1f8fe67b61f82bbdb8d3"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.34.13"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "cpe": "cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "1.35.0"
                      },
                      {
                        "fixed": "1.35.8"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "cpe": "cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "1.36.0"
                      },
                      {
                        "fixed": "1.36.5"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "cpe": "cpe:2.3:a:envoyproxy:envoy:1.37.0:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "1.37.0"
                      },
                      {
                        "last_affected": "1.37.0"
                      }
                    ],
                    "source": "CPE_STRING"
                  }
                ]
              }
            }
          ],
          "versions": [
            "1.37.0",
            "v1.37.0",
            "v1.34.12",
            "v1.36.4",
            "v1.36.3",
            "v1.34.11",
            "v1.35.7",
            "v1.34.10",
            "v1.35.6",
            "v1.36.2",
            "v1.36.1",
            "v1.35.5",
            "v1.34.9",
            "v1.36.0",
            "v1.35.4",
            "v1.34.8",
            "v1.35.3",
            "v1.34.7",
            "v1.35.2",
            "v1.34.6",
            "v1.34.5",
            "v1.35.1",
            "v1.34.4",
            "v1.35.0",
            "v1.34.3",
            "v1.34.2",
            "v1.34.1",
            "v1.34.0",
            "v1.33.0",
            "v1.32.0",
            "v1.31.0",
            "v1.30.0",
            "v1.29.0",
            "v1.28.0",
            "v1.27.0",
            "v1.26.0",
            "v1.25.0",
            "v1.24.0",
            "v1.23.0",
            "v1.22.0",
            "v1.21.0",
            "v1.20.0",
            "v1.19.0",
            "v1.18.2",
            "v1.18.1",
            "v1.18.0",
            "v1.17.0",
            "v1.16.0",
            "v1.15.0",
            "v1.14.0",
            "v1.13.0",
            "v1.12.0",
            "v1.11.0",
            "v1.10.0",
            "v1.9.0",
            "v1.8.0",
            "v1.7.0",
            "v1.6.0",
            "v1.5.0",
            "v1.4.0",
            "v1.3.0",
            "v1.2.0",
            "v1.1.0",
            "v1.0.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-26309.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:49.790966504Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/26xxx/CVE-2026-26309.json",
        "https://github.com/envoyproxy/envoy/security/advisories/GHSA-56cj-wgg3-x943",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-26309"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-193"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/26xxx/CVE-2026-26309.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-26309",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 518327,
  "published_at": "2026-03-10T19:04:21.384+00:00"
}