{
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              "matchCriteriaId": "A9D1F9A7-8359-4C3F-9932-4A085094F388",
              "versionEndExcluding": "4.7.9",
              "versionStartIncluding": "4.0.0",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, the `@partial-block` special variable is stored in the template data context and is reachable and mutable from within a template via helpers that accept arbitrary objects. When a helper overwrites `@partial-block` with a crafted Handlebars AST, a subsequent invocation of `{{\u003e @partial-block}}` compiles and executes that AST, enabling arbitrary JavaScript execution on the server. Version 4.7.9 fixes the issue. Some workarounds are available. First, use the runtime-only build (`require(\u0027handlebars/runtime\u0027)`). The `compile()` method is  absent, eliminating the vulnerable fallback path. Second, audit registered helpers for any that write arbitrary values to context objects. Helpers  should treat context data as read-only. Third, avoid registering helpers from third-party packages (such as `handlebars-helpers`) in  contexts where templates or context data can be influenced by untrusted input."
    }
  ],
  "id": "CVE-2026-33938",
  "lastModified": "2026-03-31T20:16:27.767",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 8.1,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 5.9,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-03-27T21:17:27.587",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-94"
        },
        {
          "lang": "en",
          "value": "CWE-843"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

{
  "document": {
    "category": "csaf_vex",
    "csaf_version": "2.0",
    "distribution": {
      "text": "Public",
      "tlp": {
        "label": "WHITE",
        "url": "https://www.first.org/tlp/"
      }
    },
    "lang": "en-US",
    "notes": [
      {
        "category": "general",
        "text": "To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle",
        "title": "Additional Resources"
      },
      {
        "category": "legal_disclaimer",
        "text": "The information provided in the Microsoft Knowledge Base is provided \\\"as is\\\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.",
        "title": "Disclaimer"
      }
    ],
    "publisher": {
      "category": "vendor",
      "contact_details": "secure@microsoft.com",
      "name": "Microsoft Security Response Center",
      "namespace": "https://msrc.microsoft.com"
    },
    "references": [
      {
        "category": "self",
        "summary": "CVE-2026-33938 Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block - VEX",
        "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-33938.json"
      },
      {
        "category": "external",
        "summary": "Microsoft Support Lifecycle",
        "url": "https://support.microsoft.com/lifecycle"
      },
      {
        "category": "external",
        "summary": "Common Vulnerability Scoring System",
        "url": "https://www.first.org/cvss"
      }
    ],
    "title": "Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block",
    "tracking": {
      "current_release_date": "2026-03-31T01:03:02.000Z",
      "generator": {
        "date": "2026-03-31T07:11:03.691Z",
        "engine": {
          "name": "MSRC Generator",
          "version": "1.0"
        }
      },
      "id": "msrc_CVE-2026-33938",
      "initial_release_date": "2026-03-02T00:00:00.000Z",
      "revision_history": [
        {
          "date": "2026-03-31T01:03:02.000Z",
          "legacy_version": "1",
          "number": "1",
          "summary": "Information published."
        }
      ],
      "status": "final",
      "version": "1"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "branches": [
              {
                "category": "product_version",
                "name": "2.0",
                "product": {
                  "name": "CBL Mariner 2.0",
                  "product_id": "17086"
                }
              }
            ],
            "category": "product_name",
            "name": "Azure Linux"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "cbl2 reaper 3.1.1-22",
                "product": {
                  "name": "cbl2 reaper 3.1.1-22",
                  "product_id": "1"
                }
              }
            ],
            "category": "product_name",
            "name": "reaper"
          }
        ],
        "category": "vendor",
        "name": "Microsoft"
      }
    ],
    "relationships": [
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        "category": "default_component_of",
        "full_product_name": {
          "name": "cbl2 reaper 3.1.1-22 as a component of CBL Mariner 2.0",
          "product_id": "17086-1"
        },
        "product_reference": "1",
        "relates_to_product_reference": "17086"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-33938",
      "cwe": {
        "id": "CWE-94",
        "name": "Improper Control of Generation of Code (\u0027Code Injection\u0027)"
      },
      "notes": [
        {
          "category": "general",
          "text": "GitHub_M",
          "title": "Assigning CNA"
        }
      ],
      "product_status": {
        "known_affected": [
          "17086-1"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "CVE-2026-33938 Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block - VEX",
          "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-33938.json"
        }
      ],
      "remediations": [
        {
          "category": "none_available",
          "date": "2026-03-31T01:03:02.000Z",
          "details": "There is no fix available for this vulnerability as of now",
          "product_ids": [
            "17086-1"
          ]
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 8.1,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "environmentalsScore": 0.0,
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "temporalScore": 8.1,
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "products": [
            "17086-1"
          ]
        }
      ],
      "title": "Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block"
    }
  ]
}

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.7.8"
      },
      "package": {
        "ecosystem": "npm",
        "name": "handlebars"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.0.0"
            },
            {
              "fixed": "4.7.9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-33938"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-843",
      "CWE-94"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-27T18:20:44Z",
    "nvd_published_at": "2026-03-27T21:17:27Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nThe `@partial-block` special variable is stored in the template data context and is reachable and mutable from within a template via helpers that accept arbitrary objects. When a helper overwrites `@partial-block` with a crafted Handlebars AST, a subsequent invocation of `{{\u003e @partial-block}}` compiles and executes that AST, enabling arbitrary JavaScript execution on the server.\n\n## Description\n\nHandlebars stores `@partial-block` in the `data` frame that is accessible to templates. In nested contexts, a parent frame\u0027s `@partial-block` is reachable as `@_parent.partial-block`. Because the data frame is a mutable object, any registered helper that accepts an object reference and assigns properties to it can overwrite `@partial-block` with an attacker-controlled value.\n\nWhen `{{\u003e @partial-block}}` is subsequently evaluated, `invokePartial` receives the crafted object. The runtime, finding an object that is not a compiled function, falls back to **dynamically compiling** the value via `env.compile()`. If that value is a well-formed Handlebars AST containing injected code, the injected JavaScript runs in the server process.\n\nThe `handlebars-helpers` npm package (commonly used with Handlebars) includes several helpers such as `merge` that can be used as the mutation primitive.\n\n## Proof of Concept\n\nTested with Handlebars 4.7.8 and `handlebars-helpers`:\n\n```javascript\nconst Handlebars = require(\u0027handlebars\u0027);\nconst merge = require(\u0027handlebars-helpers\u0027).object().merge;\nHandlebars.registerHelper(\u0027merge\u0027, merge);\n\nconst vulnerableTemplate = `\n{{#*inline \"myPartial\"}}\n    {{\u003e@partial-block}}\n    {{\u003e@partial-block}}\n{{/inline}}\n{{#\u003emyPartial}}\n    {{merge @_parent partial-block=1}}\n    {{merge @_parent partial-block=payload}}\n{{/myPartial}}\n`;\n\nconst maliciousContext = {\n  payload: {\n    type: \"Program\",\n    body: [\n      {\n        type: \"MustacheStatement\",\n        depth: 0,\n        path: {\n          type: \"PathExpression\",\n          parts: [\"pop\"],\n          original: \"this.pop\",\n          // Code injected via depth field \u2014 breaks out of generated function call\n          depth: \"0])),function () {console.error(\u0027VULNERABLE: RCE via @partial-block\u0027);}()));//\",\n        },\n      },\n    ],\n  },\n};\n\nHandlebars.compile(vulnerableTemplate)(maliciousContext);\n// Prints: VULNERABLE: RCE via @partial-block\n```\n\n## Workarounds\n\n- **Use the runtime-only build** (`require(\u0027handlebars/runtime\u0027)`). The `compile()` method is  absent, eliminating the vulnerable fallback path.\n- **Audit registered helpers** for any that write arbitrary values to context objects. Helpers  should treat context data as read-only.\n- **Avoid registering helpers** from third-party packages (such as `handlebars-helpers`) in  contexts where templates or context data can be influenced by untrusted input.",
  "id": "GHSA-3mfm-83xf-c92r",
  "modified": "2026-03-27T21:52:26Z",
  "published": "2026-03-27T18:20:44Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33938"
    },
    {
      "type": "WEB",
      "url": "https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/handlebars-lang/handlebars.js"
    },
    {
      "type": "WEB",
      "url": "https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block"
}