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Vulnerability details: VCID-2vdk-f8x9-wqbb
Vulnerability ID VCID-2vdk-f8x9-wqbb
Aliases CVE-2026-33938
GHSA-3mfm-83xf-c92r
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 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.
Status Published
Exploitability 0.5
Weighted Severity 8.0
Risk 4.0
Affected and Fixed Packages Package Details
Weaknesses (5)
System Score Found at
cvssv3 8.1 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2026-33938.json
epss 0.00048 https://api.first.org/data/v1/epss?cve=CVE-2026-33938
epss 0.00048 https://api.first.org/data/v1/epss?cve=CVE-2026-33938
epss 0.00048 https://api.first.org/data/v1/epss?cve=CVE-2026-33938
epss 0.00048 https://api.first.org/data/v1/epss?cve=CVE-2026-33938
cvssv3.1_qr HIGH https://github.com/advisories/GHSA-3mfm-83xf-c92r
cvssv3.1 8.1 https://github.com/handlebars-lang/handlebars.js
generic_textual HIGH https://github.com/handlebars-lang/handlebars.js
cvssv3.1 8.1 https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2
generic_textual HIGH https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2
ssvc Track* https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2
cvssv3.1 8.1 https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9
generic_textual HIGH https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9
ssvc Track* https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9
cvssv3.1 8.1 https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r
cvssv3.1_qr HIGH https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r
generic_textual HIGH https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r
ssvc Track* https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r
cvssv3.1 8.1 https://nvd.nist.gov/vuln/detail/CVE-2026-33938
generic_textual HIGH https://nvd.nist.gov/vuln/detail/CVE-2026-33938
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2026-33938.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

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Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://github.com/handlebars-lang/handlebars.js
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

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Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

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Vector: SSVCv2/E:P/A:N/T:T/P:M/B:A/M:M/D:R/2026-03-31T18:39:18Z/ Found at https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

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Vector: SSVCv2/E:P/A:N/T:T/P:M/B:A/M:M/D:R/2026-03-31T18:39:18Z/ Found at https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

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none


Vector: SSVCv2/E:P/A:N/T:T/P:M/B:A/M:M/D:R/2026-03-31T18:39:18Z/ Found at https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://nvd.nist.gov/vuln/detail/CVE-2026-33938
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

Exploit Prediction Scoring System (EPSS)
Percentile 0.15224
EPSS Score 0.00048
Published At June 11, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-06-11T16:49:44.844082+00:00 Vulnrichment Import https://github.com/cisagov/vulnrichment/blob/develop/2026/33xxx/CVE-2026-33938.json 38.6.0