{"id":"CVE-2026-33939","revision":null,"records":[{"revision":"69441d1f6a7b473885abeb857584064c","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-33939","aliases":[],"title":"Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation","description":"Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, when a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. `{{*n}}`), the compiled template calls `lookupProperty(decorators, \"n\")`, which returns `undefined`. The runtime then immediately invokes the result as a function, causing an unhandled `TypeError: ... is not a function` that crashes the Node.js process. Any application that compiles user-supplied templates without wrapping the call in a `try/catch` is vulnerable to a single-request Denial of Service. Version 4.7.9 fixes the issue. Some workarounds are available. Wrap compilation and rendering in `try/catch`. Validate template input before passing it to `compile()`; reject templates containing  decorator syntax (`{{*...}}`) if decorators are not used in your application. Use the pre-compilation workflow; compile templates at build time and serve only pre-compiled  templates; do not call `compile()` at request time.","state":0,"publishedAt":"2026-03-27T21:08:24.664+00:00","modifiedAt":"2026-09-04T12:04:44.445+00:00","affected":[{"ecosystem":"Vendor product","name":"handlebars.js","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"handlebars-lang\",\n                    \"product\": \"handlebars.js\",\n                    \"versions\": [\n                        {\n                            \"version\": \">= 4.0.0, < 4.7.9\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":"HIGH"}],"references":["https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-9cx6-37pm-9jff","https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-33939","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-33939","identifiers":["CVE-2026-33939"]},"retained":false,"historicalAffected":[]},{"revision":"8e8eff58092d4e9598c1de968e70c33e","observedAt":"2026-11-01T06:05:00.137+00:00","statement":{"source":"euvd","id":"EUVD-2026-16858","aliases":["CVE-2026-33939"],"title":"Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, when a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. `{{*n}}`), the compiled templat…","description":"Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, when a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. `{{*n}}`), the compiled template calls `lookupProperty(decorators, \"n\")`, which returns `undefined`. The runtime then immediately invokes the result as a function, causing an unhandled `TypeError: ... is not a function` that crashes the Node.js process. Any application that compiles user-supplied templates without wrapping the call in a `try/catch` is vulnerable to a single-request Denial of Service. Version 4.7.9 fixes the issue. Some workarounds are available. Wrap compilation and rendering in `try/catch`. Validate template input before passing it to `compile()`; reject templates containing  decorator syntax (`{{*...}}`) if decorators are not used in your application. Use the pre-compilation workflow; compile templates at build time and serve only pre-compiled  templates; do not call `compile()` at request time.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":null}],"references":["https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-9cx6-37pm-9jff","https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-16858","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Mar 27, 2026, 9:08:24 PM","dateUpdated":"Sep 4, 2026, 12:04:44 PM"},"relatedAdvisories":[{"id":"RHSA-2026:34342","title":"Red Hat Security Advisory: Cluster Observability Operator 1.5.0","vulnerabilityIds":["CVE-2020-7753","CVE-2021-33623","CVE-2024-4068","CVE-2024-45338","CVE-2024-52011","CVE-2025-22868","CVE-2025-22870","CVE-2025-22872","CVE-2025-47911","CVE-2025-58190","CVE-2026-1526","CVE-2026-1528","CVE-2026-2229","CVE-2026-4800","CVE-2026-4867","CVE-2026-6321","CVE-2026-6322","CVE-2026-6734","CVE-2026-9277","CVE-2026-9697","CVE-2026-12143","CVE-2026-12151","CVE-2026-25680","CVE-2026-25681","CVE-2026-29063","CVE-2026-32141","CVE-2026-33228","CVE-2026-33671","CVE-2026-33814","CVE-2026-33891","CVE-2026-33894","CVE-2026-33895","CVE-2026-33896","CVE-2026-33937","CVE-2026-33938","CVE-2026-33939","CVE-2026-33940","CVE-2026-33941","CVE-2026-39821","CVE-2026-42506","CVE-2026-48779"]},{"id":"msrc_CVE-2026-33939","title":"Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation","vulnerabilityIds":["CVE-2026-33939"]},{"id":"RHSA-2026:10175","title":"Red Hat Security Advisory: Red Hat OpenShift Dev Spaces 3.27.1 Release.","vulnerabilityIds":["CVE-2025-61728","CVE-2025-62718","CVE-2026-2332","CVE-2026-4800","CVE-2026-4926","CVE-2026-22731","CVE-2026-25679","CVE-2026-26999","CVE-2026-27137","CVE-2026-27606","CVE-2026-29054","CVE-2026-32305","CVE-2026-32695","CVE-2026-33186","CVE-2026-33433","CVE-2026-33805","CVE-2026-33870","CVE-2026-33871","CVE-2026-33937","CVE-2026-33938","CVE-2026-33939","CVE-2026-33940","CVE-2026-33941","CVE-2026-34986","CVE-2026-40175"]}],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-16858","identifiers":["EUVD-2026-16858","CVE-2026-33939"]},"retained":false,"historicalAffected":[]},{"revision":"dfc621c4e7df44c5b6af125a7617e3d8","observedAt":"2026-10-27T09:03:00.507+00:00","statement":{"source":"nvd","id":"CVE-2026-33939","aliases":[],"title":"Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, when a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. `{{*n}}`), the compiled templat…","description":"Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, when a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. `{{*n}}`), the compiled template calls `lookupProperty(decorators, \"n\")`, which returns `undefined`. The runtime then immediately invokes the result as a function, causing an unhandled `TypeError: ... is not a function` that crashes the Node.js process. Any application that compiles user-supplied templates without wrapping the call in a `try/catch` is vulnerable to a single-request Denial of Service. Version 4.7.9 fixes the issue. Some workarounds are available. Wrap compilation and rendering in `try/catch`. Validate template input before passing it to `compile()`; reject templates containing  decorator syntax (`{{*...}}`) if decorators are not used in your application. Use the pre-compilation workflow; compile templates at build time and serve only pre-compiled  templates; do not call `compile()` at request time.","state":0,"publishedAt":"2026-03-27T22:16:20.857+00:00","modifiedAt":"2026-10-26T22:10:00.163+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · security-advisories@github.com · Secondary","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":"HIGH"},{"system":"CVSS 3.1 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c · Secondary","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":"HIGH"}],"references":["https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9","https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-9cx6-37pm-9jff","https://access.redhat.com/errata/RHSA-2026:10175","https://access.redhat.com/errata/RHSA-2026:34342","https://access.redhat.com/security/cve/CVE-2026-33939","https://bugzilla.redhat.com/show_bug.cgi?id=2452508","https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33939.json"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-33939","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Modified","weaknesses":["CWE-754","CWE-248"],"productCriteria":["cpe:2.3:a:handlebarsjs:handlebars:*:*:*:*:*:node.js:*:*"],"sourceDates":{"published":"2026-03-27T22:16:20.857","lastModified":"2026-10-26T22:10:00.163"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-33939","identifiers":["CVE-2026-33939"]},"retained":false,"historicalAffected":[]},{"revision":"ea1fb7732f3a431b941ce385102b1815","observedAt":"2026-10-24T13:17:17.793+00:00","statement":{"source":"osv","id":"GHSA-9cx6-37pm-9jff","aliases":["CVE-2026-33939"],"title":"Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation","description":"## Summary\n\nWhen a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. `{{*n}}`), the compiled template calls `lookupProperty(decorators, \"n\")`, which returns `undefined`. The runtime then immediately invokes the result as a function, causing an unhandled `TypeError: ... is not a function` that crashes the Node.js process. Any application that compiles user-supplied templates without wrapping the call in a `try/catch` is vulnerable to a single-request Denial of Service.\n\n## Description\n\nIn `lib/handlebars/compiler/javascript-compiler.js`, the code generated for a decorator invocation looks like:\n\n```javascript\nfn = lookupProperty(decorators, \"n\")(fn, props, container, options) || fn;\n```\n\nWhen `\"n\"` is not a registered decorator, `lookupProperty(decorators, \"n\")` returns `undefined`. The expression immediately attempts to call `undefined` as a function, producing:\n\n```\nTypeError: lookupProperty(...) is not a function\n```\n\nBecause the error is thrown inside the compiled template function and is not caught by the runtime, it propagates up as an unhandled exception and — when not caught by the application — crashes the Node.js process.\n\nThis inconsistency is notable: references to unregistered **helpers** produce a clean `\"Missing helper: ...\"` error, while references to unregistered **decorators** cause a hard crash.\n\n**Attack scenario:** An attacker submits `{{*n}}` as template content to any endpoint that calls `Handlebars.compile(userInput)()`. Each request crashes the server process; with process managers that auto-restart (PM2, systemd), repeated submissions create a persistent DoS.\n\n## Proof of Concept\n\n```javascript\nconst Handlebars = require('handlebars'); // Handlebars 4.7.8, Node.js v22.x\n\n// Any of these payloads crash the process\nHandlebars.compile('{{*n}}')({});\nHandlebars.compile('{{*decorator}}')({});\nHandlebars.compile('{{*constructor}}')({});\n```\n\nExpected crash output:\n```\nTypeError: lookupProperty(...) is not a function\n    at Function.eval [as decorator] (eval at compile (...javascript-compiler.js:134:36))\n```\n\n## Workarounds\n\n- **Wrap compilation and rendering in `try/catch`:**\n  ```javascript\n  try {\n    const result = Handlebars.compile(userInput)(context);\n    res.send(result);\n  } catch (err) {\n    res.status(400).send('Invalid template');\n  }\n  ```\n- **Validate template input** before passing it to `compile()`. Reject templates containing  decorator syntax (`{{*...}}`) if decorators are not used in your application.\n- **Use the pre-compilation workflow:** compile templates at build time and serve only pre-compiled  templates; do not call `compile()` at request time.","state":0,"publishedAt":"2026-03-27T18:21:15+00:00","modifiedAt":"2026-09-10T03:51:00.150731+00:00","affected":[{"ecosystem":"npm","name":"handlebars","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"4.0.0"},{"kind":"fixed","version":"4.7.9"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"HIGH"}],"references":["https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-9cx6-37pm-9jff","https://nvd.nist.gov/vuln/detail/CVE-2026-33939","https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","https://github.com/handlebars-lang/handlebars.js","https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9"],"sourceUrl":"https://github.com/advisories/GHSA-9cx6-37pm-9jff","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-9cx6-37pm-9jff","identifiers":["GHSA-9cx6-37pm-9jff","CVE-2026-33939"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. Missing entries do not establish absence of exploitation.","generation":"2026-11-01T11:57:48.0676708+00:00","complete":true,"records":1766,"lastAttemptAt":"2026-11-01T11:57:48.0676708+00:00","lastSuccessAt":"2026-11-01T11:57:48.2627764+00:00","error":null,"lastVerifiedAt":"2026-11-01T11:57:48.2627778+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"cve-program","scope":"Official CVE Program baseline and cumulative hourly delta; all vendors, published and rejected records","generation":"cve-aece262bb10a694367a43c24d730aa8e8dc171723eaec4c15cdd32f04bda103f-9f544fe753c0f8392473253b79bdd66e19fccf5dd53b170273049f860eb7c038","complete":true,"records":417646,"lastAttemptAt":"2026-11-01T11:57:47.5724102+00:00","lastSuccessAt":"2026-11-01T11:57:47.5551783+00:00","error":null,"lastVerifiedAt":"2026-11-01T11:57:47.5724102+00:00","snapshotPublishedAt":"2026-11-01T11:25:34+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"euvd","scope":"Rolling EUVD lookups of CVE aliases in current public OSV archives; 500 identifiers per refresh, rechecked after 48 hours. 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