{"id":"CVE-2026-33937","state":"PUBLISHED","title":"Handlebars.js has JavaScript Injection via AST Type Confusion","description":"Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, `Handlebars.compile()` accepts a pre-parsed AST object in addition to a template string. The `value` field of a `NumberLiteral` AST node is emitted directly into the generated JavaScript without quoting or sanitization. An attacker who can supply a crafted AST to `compile()` can therefore inject and execute arbitrary JavaScript, leading to Remote Code Execution on the server. Version 4.7.9 fixes the issue. Some workarounds are available. Validate input type before calling `Handlebars.compile()`; ensure the argument is always a  `string`, never a plain object or JSON-deserialized value. Use the Handlebars runtime-only build (`handlebars/runtime`) on the server if templates are pre-compiled at build time; `compile()` will be unavailable.","publishedAt":"2026-03-27T21:03:46.748Z","updatedAt":"2026-09-04T12:04:45.273Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"GitHub_M"},"assigner":"GitHub_M","products":["handlebars-lang handlebars.js"],"affected":[{"vendor":"handlebars-lang","product":"handlebars.js","versions":[{"version":">= 4.0.0, < 4.7.9","status":"affected"}]}],"references":["https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-2w6w-674q-4c4q","https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9","https://access.redhat.com/security/cve/CVE-2026-33937","https://bugzilla.redhat.com/show_bug.cgi?id=2452523","https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33937.json","https://access.redhat.com/errata/RHSA-2026:34342","https://access.redhat.com/errata/RHSA-2026:10175"],"weaknesses":["CWE-843","CWE-94"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/33xxx/CVE-2026-33937.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-33937","state":"PUBLISHED","datePublished":"2026-03-27T21:03:46.748Z","dateUpdated":"2026-09-04T12:04:45.273Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-03-24T19:50:52.103Z"},"containers":{"cna":{"title":"Handlebars.js has JavaScript Injection via AST Type Confusion","descriptions":[{"lang":"en","value":"Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, `Handlebars.compile()` accepts a pre-parsed AST object in addition to a template string. The `value` field of a `NumberLiteral` AST node is emitted directly into the generated JavaScript without quoting or sanitization. An attacker who can supply a crafted AST to `compile()` can therefore inject and execute arbitrary JavaScript, leading to Remote Code Execution on the server. Version 4.7.9 fixes the issue. Some workarounds are available. Validate input type before calling `Handlebars.compile()`; ensure the argument is always a  `string`, never a plain object or JSON-deserialized value. Use the Handlebars runtime-only build (`handlebars/runtime`) on the server if templates are pre-compiled at build time; `compile()` will be unavailable."}],"affected":[{"vendor":"handlebars-lang","product":"handlebars.js","versions":[{"version":">= 4.0.0, < 4.7.9","status":"affected"}]}],"references":[{"url":"https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-2w6w-674q-4c4q","name":"https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-2w6w-674q-4c4q","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","name":"https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","tags":["x_refsource_MISC"]},{"url":"https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9","name":"https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9","tags":["x_refsource_MISC"]}],"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":[{"descriptions":[{"cweId":"CWE-843","lang":"en","description":"CWE-843: Access of Resource Using Incompatible Type ('Type Confusion')","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-94","lang":"en","description":"CWE-94: Improper Control of Generation of Code ('Code Injection')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-03-27T21:03:46.748Z"},"source":{"advisory":"GHSA-2w6w-674q-4c4q","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-03-31T00:00:00+00:00","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3","id":"CVE-2026-33937"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-04-01T03:55:43.931Z"}},{"title":"handlebars.js: Handlebars: Remote Code Execution via crafted Abstract Syntax Tree object in compile()","descriptions":[{"lang":"en","value":"A flaw was found in Handlebars. An attacker can exploit this by supplying a crafted Abstract Syntax Tree (AST) object to the `Handlebars.compile()` function. This allows the injection and execution of arbitrary JavaScript code due to improper sanitization of the `value` field in `NumberLiteral` AST nodes. This vulnerability can lead to Remote Code Execution (RCE) on the server."}],"affected":[{"vendor":"Red Hat","product":"Cluster Observability Operator 1.5.0","packageName":"cluster-observability-operator/logging-console-plugin-pf4-rhel9","defaultStatus":"affected","versions":[{"version":"1782839279","status":"unaffected","lessThan":"*","versionType":"rpm"}],"collectionURL":"https://catalog.redhat.com/software/containers/","cpes":["cpe:/a:redhat:cluster_observability_operator:1.5::el9"]},{"vendor":"Red Hat","product":"Cluster Observability Operator 1.5.0","packageName":"cluster-observability-operator/logging-console-plugin-pf5-rhel9","defaultStatus":"affected","versions":[{"version":"1782840539","status":"unaffected","lessThan":"*","versionType":"rpm"}],"collectionURL":"https://catalog.redhat.com/software/containers/","cpes":["cpe:/a:redhat:cluster_observability_operator:1.5::el9"]},{"vendor":"Red Hat","product":"Cluster Observability Operator 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Hat."},{"lang":"en","time":"2026-03-27T21:03:46.748Z","value":"Made public."}],"workarounds":[{"lang":"en","value":"To mitigate this issue, ensure that any input provided to the `Handlebars.compile()` function is strictly validated to be a string type, preventing the injection of crafted Abstract Syntax Tree (AST) objects. Additionally, for deployments where templates are pre-compiled at build time, consider utilizing the Handlebars runtime-only build (`handlebars/runtime`). This build variant does not include the `compile()` function, thereby eliminating the attack vector. If the application is a service, a restart may be required for the changes to take effect."}],"x_adpType":"supplier","x_generator":{"engine":"sadp-cli 1.0.0"}}]}}}