CVE-2026-33940: handlebars.js · Code Injection
Affects handlebars.jsSource CVE Database V5
Not known to be exploited · CVSS 8.1 High : upgrade to 4.7.9 soon.
Data as of 30 Oct 2026, 11:52 UTC
- EPSS
- 0.7% chance of exploitation in 30 days – higher than 53% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 4.7.9
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 27 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Upgrade handlebars.js to 4.7.9.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| handlebars-langhandlebars.js | Affected
| Fixed in
|
npmhandlebarspkg:npm/handlebarsOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
An official fix is available in Handlebars.js version 4.7.9. Users should upgrade to this version to remediate the vulnerability. If upgrading immediately is not possible, apply workarounds: use the runtime-only build to avoid fallback compilation paths, sanitize all context data to ensure no non-primitive objects can be passed as dynamic partials, and avoid dynamic partial lookups when context data is user-controlled.
Description
Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, a crafted object placed in the template context can bypass all conditional guards in `resolvePartial()` and cause `invokePartial()` to return `undefined`. The Handlebars runtime then treats the unresolved partial as a source that needs to be compiled, passing the crafted object to `env.compile()`. Because the object is a valid Handlebars AST containing injected code, the generated JavaScript executes arbitrary commands on the server. The attack requires the adversary to control a value that can be returned by a dynamic partial lookup. Version 4.7.9 fixes the issue. Some workarounds are available. First, use the runtime-only build (`require('handlebars/runtime')`). Without `compile()`, the fallback compilation path in `invokePartial` is unreachable. Second, sanitize context data before rendering: Ensure no value in the context is a non-primitive object that could be passed to a dynamic partial. Third, avoid dynamic partial lookups (`{{> (lookup ...)}}`) when context data is user-controlled.
References
- github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-xhpv-hc6g-r9c6 (opens in a new tab)
- github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2 (opens in a new tab)
- github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9 (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-33940 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2452521 (opens in a new tab)
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33940.json (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:34342 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:10175 (opens in a new tab)