{"id":"CVE-2026-33938","title":"Handlebars provides the power necessary to let users build semantic templates","summary":"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 templ…","severity":"high","cvss":8.1,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","cwe":["CWE-94","CWE-843","CWE-917"],"vendor":"handlebarsjs","product":"handlebars","affected":["handlebars >= 4.0.0, < 4.7.9"],"patched":["handlebars 4.7.9"],"published":"2026-03-27","updated":"2026-07-02","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-33938","references":[{"url":"https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","label":"security-advisories@github.com"},{"url":"https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9","label":"security-advisories@github.com"},{"url":"https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r","label":"security-advisories@github.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:10175","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:34342","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/security/cve/CVE-2026-33938","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2452525","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33938.json","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-33938"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33938"}],"tags":["nvd","csaf","vex","red-hat"],"epss":0.00721,"epssPercentile":0.53754,"ingestedAt":"2026-07-02T12:34:40.406Z","slug":"CVE-2026-33938","body":"## Overview\n\nHandlebars 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 `{{> @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('handlebars/runtime')`). 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.\n\n## Affected\n\n- `handlebars >= 4.0.0, < 4.7.9`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `handlebars 4.7.9`\n\n## Vendor advisories\n\n- **RHSA-2026:34342** · Red Hat · fixed in: Cluster Observability Operator 1.5.3 · released 2026-07-01 · [advisory](https://access.redhat.com/errata/RHSA-2026:34342)\n- **RHSA-2026:10175** · Red Hat · fixed in: Red Hat OpenShift Dev Spaces 3.27 · released 2026-04-23 · [advisory](https://access.redhat.com/errata/RHSA-2026:10175)\n- **Red Hat VEX** · Important · affected: Logging Subsystem for Red Hat OpenShift, Red Hat Developer Hub, Red Hat Enterprise Linux 8 · no fix planned: Logging Subsystem for Red Hat OpenShift, Red Hat Enterprise Linux 8, Red Hat Developer Hub · updated 2026-10-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33938.json)","depth":"twilight","depthScore":45,"depthScoreParts":{"impact":44.6,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}