CVE-2026-33939

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{"bugzilla": {"description": "handlebars.js: Handlebars.js: Denial of Service via malformed decorator syntax in template compilation", "id": "2452508", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2452508"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-248", "details": ["A flaw was found in Handlebars.js. A remote attacker can exploit this by submitting a malformed Handlebars template that includes decorator syntax referencing an unregistered decorator. When the application attempts to compile this template without proper error handling, it triggers an unhandled `TypeError`. This error causes the Node.js process to crash, resulting in a Denial of Service (DoS) for the affected application."], "mitigation": {"lang": "en:us", "value": "To mitigate this issue, applications utilizing Handlebars.js should implement robust error handling during template compilation and rendering. Specifically, wrap template compilation and rendering calls in `try/catch` blocks to gracefully handle `TypeError` exceptions. Alternatively, validate user-supplied template input to reject decorator syntax (`{{*...}}`) if decorators are not actively used by the application. Employing a pre-compilation workflow, where templates are compiled at build time and only pre-compiled templates are served, can also prevent runtime exploitation. If the application is a service, a restart may be required for changes to take effect."}, "name": "CVE-2026-33939", "package_state": [{"cpe": "cpe:/a:redhat:cryostat:4", "fix_state": "Affected", "package_name": "handlebars", "product_name": "Cryostat 4"}, {"cpe": "cpe:/a:redhat:logging:5", "fix_state": "Affected", "package_name": "openshift-logging/elasticsearch6-rhel9", "product_name": "Logging Subsystem for Red Hat OpenShift"}, {"cpe": "cpe:/a:redhat:logging:5", "fix_state": "Affected", "package_name": "openshift-logging/elasticsearch-operator-bundle", "product_name": "Logging Subsystem for Red Hat OpenShift"}, {"cpe": "cpe:/a:redhat:logging:5", "fix_state": "Affected", "package_name": "openshift-logging/elasticsearch-proxy-rhel9", "product_name": "Logging Subsystem for Red Hat OpenShift"}, {"cpe": "cpe:/a:redhat:logging:5", "fix_state": "Affected", "package_name": "openshift-logging/elasticsearch-rhel9-operator", "product_name": "Logging Subsystem for Red Hat OpenShift"}, {"cpe": "cpe:/a:redhat:logging:5", "fix_state": "Affected", "package_name": "openshift-logging/kibana6-rhel8", "product_name": "Logging Subsystem for Red Hat OpenShift"}, {"cpe": "cpe:/a:redhat:logging:5", "fix_state": "Affected", "package_name": "openshift-logging/logging-curator5-rhel9", "product_name": "Logging Subsystem for Red Hat OpenShift"}, {"cpe": "cpe:/a:redhat:jboss_data_grid:8", "fix_state": "Affected", "package_name": "handlebars", "product_name": "Red Hat Data Grid 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "firefox", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "thunderbird", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "firefox", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "389-ds:1.4/389-ds-base", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "firefox", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "grafana", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "mozjs60", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "thunderbird", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "firefox", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "thunderbird", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Affected", "package_name": "rhoai/odh-workbench-codeserver-datascience-cpu-py312-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_devspaces:3", "fix_state": "Affected", "package_name": "devspaces/code-rhel9", "product_name": "Red Hat OpenShift Dev Spaces"}, {"cpe": "cpe:/a:redhat:jboss_enterprise_bpms_platform:7", "fix_state": "Affected", "package_name": "handlebars", "product_name": "Red Hat Process Automation 7"}], "public_date": "2026-03-27T21:08:24Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-33939\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-33939\nhttps://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2\nhttps://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9\nhttps://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-9cx6-37pm-9jff"], "statement": "This is an Important denial of service flaw in Handlebars.js affecting applications that compile user-supplied templates without proper error handling. A remote attacker can submit a malformed template containing unregistered decorator syntax, leading to an unhandled `TypeError` and crashing the Node.js process. Red Hat products are vulnerable if they use Handlebars.js in a configuration that allows untrusted input to be compiled at runtime without implementing `try/catch` blocks or input validation.", "threat_severity": "Important"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[4.0.0,4.7.9)"}}], "enrichment": {"confidence": 81.0, "confidence_source": "matching", "scores": [{"score": 81.0, "source": "matching"}]}, "original": {"product": "handlebars.js", "source": "cna", "vendor": "handlebars-lang"}, "product": "handlebars", "vendor": "handlebarsjs"}], "analysis": {"en": {"generated_at": "2026-03-31T19:41:59.734943+00:00", "value": {"mitigation_remediation": ["Update Handlebars to version 4.7.9 or later", "Wrap calls to compile() and rendering in try/catch blocks", "Validate template input before compilation; reject any template containing decorator syntax if decorators are not used", "Adopt a pre\u2011compilation workflow to compile templates offline and serve only pre\u2011compiled templates", "Check the vendor\u2019s website for additional patches or updates"], "summary": {"action": "Patch", "impact": "Denial of Service"}, "threat_synthesis": {"affected_systems": "Handlbars.js versions 4.0.0 through 4.7.8 from the handlebars-lang project are affected. Any Node.js application that compiles user-supplied templates using these versions without proper safeguards is at risk. The flaw was remedied in version 4.7.9.", "description_and_impact": "The vulnerability occurs when a Handlebars template contains decorator syntax that references an unregistered decorator, causing an undefined value to be invoked as a function during compilation. This triggers an unhandled TypeError, crashing the Node.js process and resulting in a denial of service. The weakness involves unexpected type usage and lack of exception handling, corresponding to common error handling failures.", "risk_and_exploitability": "Based on the CVSS score of 7.5, the flaw carries high severity, while the EPSS score of less than 1% suggests a low probability of real\u2011world exploitation. It is not listed in the CISA KEV catalog. Nonetheless, if an application compiles templates on request from untrusted input, an attacker can trigger the crash by sending a template containing malformed decorator syntax such as '{{*n}}', thereby causing repeated service interruptions. The lack of defensive coding and the potential to crash the entire process amplifies the impact of the vulnerability."}}}}, "created": "2026-03-29T20:29:49.781191+00:00", "updated": "2026-03-31T20:00:39.838564+00:00", "vendors": ["handlebarsjs", "handlebarsjs$PRODUCT$handlebars"]}