Home/CVE/Express-handlebars is a Handlebars view engine for Express. Express-handlebars mixes pure template data with engine conf
CVE
CVE-2021-32820
Express-handlebars is a Handlebars view engine for Express. Express-handlebars mixes pure template data with engine conf
Express-handlebars is a Handlebars view engine for Express. Express-handlebars mixes pure template data with engine configuration options through the Express render API. More specifically, the layout parameter may trigger file disclosure vulnerabilities in downstream applications.
This potential vulnerability is somewhat restricted in that only files with existing extentions (i.e. file.extension) can be included, files that lack an extension will have .handlebars appended to them. For complete details refer to the referenced GHSL-2021-018 report. Notes in documentation have been added to help users avoid this potential information exposure vulnerability.
HIGH · CVSS 8.6
EPSS 0.86122
Act now
- EPSS ≥ 0.50 - high probability of exploitation in the next 30 days
- EPSS percentile: top 1% of all CVEs by exploitation likelihood
- Public exploit or PoC is available
- CVSS base score ≥ 7.0
Sigma rules0
YARA rules0
Look this up elsewhere - one-click external pivots
▸
How to read a CVE - triage first, then detect and patch
This page is every public fact about CVE-2021-32820, cross-linked. Its job is to answer one question fast - does this need my attention now? - and then hand you the two things you do about it. Here is how an analyst reads it.
Triage: should I act now? Four signals, and they are not interchangeable:
CVSSseverity - how bad it is IF exploited, 0-10. A high CVSS alone is not urgency; a flaw can be a perfect 10 and never actually be attacked.
EPSSprobability - a model’s estimate of the chance it is exploited in the next 30 days, 0-1. This is the “will it actually happen” signal.
CISA KEVconfirmed - it is being exploited in the wild right now. The strongest signal on the page; KEV beats any score.
Weaponisedavailability - public exploits / PoCs, and especially Metasploit modules rated Excellent / Great. Reliable, packaged exploit code means low-skill attackers can use it today.
How they combine: KEV, or a dependable Metasploit module, means patch now regardless of CVSS. High CVSS + low EPSS + no exploit is real but not an emergency - schedule it. Low CVSS but KEV-listed still gets patched now. The verdict above already weighed these for you; this is how it got there.
Then what - two workflows:
Detectwhen you cannot patch today, follow this CVE to the ATT&CK techniques it enables, then Build a SIEM detection (the green button) - author a rule, test it in Atomic, deploy it. That buys visibility while the patch waits.
PatchAffected products / packages tell you if you are exposed; Fixed versions by distribution and Vendor advisories give the exact version that closes it.
Reading order for the panels below: verdict + badges, then Public exploits / Metasploit (is it weaponised), then ATT&CK techniques + Sigma / IDS rules (can I detect it), then Affected products / packages + Fixed versions (am I exposed, what patches it), then Threat actors / IOCs (who uses it), then Scoring & timeline / references (the evidence).
◆
ATT&CK techniques
20Techniques this CVE enables - linked via CWECAPECATT&CK. High◆ = named directly in ATT&CK or Nuclei templates.
T1007 · System Service Discovery T1016 · System Network Configuration Discovery T1018 · Remote System Discovery T1027.006 · HTML Smuggling T1027.009 · Embedded Payloads T1033 · System Owner/User Discovery T1036.005 · Match Legitimate Resource Name or Location T1046 · Network Service Discovery T1049 · System Network Connections Discovery T1057 · Process Discovery T1069 · Permission Groups Discovery T1082 · System Information Discovery T1083 · File and Directory Discovery T1087 · Account Discovery T1111 · Multi-Factor Authentication Interception T1120 · Peripheral Device Discovery T1124 · System Time Discovery T1134.001 · Token Impersonation/Theft T1135 · Network Share Discovery T1217 · Browser Information Discovery
▤ Build a SIEM detection for these techniques
▤
CAPEC attack patterns
12Attack patterns this CVE enables - the bridge from weakness to ATT&CK technique.
CAPEC-CAPEC-116 · Excavation CAPEC-CAPEC-13 · Subverting Environment Variable Values CAPEC-CAPEC-169 · Footprinting CAPEC-CAPEC-22 · Exploiting Trust in Client CAPEC-CAPEC-224 · Fingerprinting CAPEC-CAPEC-242 · Code Injection CAPEC-CAPEC-285 · ICMP Echo Request Ping CAPEC-CAPEC-287 · TCP SYN Scan CAPEC-CAPEC-290 · Enumerate Mail Exchange (MX) Records CAPEC-CAPEC-291 · DNS Zone Transfers CAPEC-CAPEC-292 · Host Discovery CAPEC-CAPEC-293 · Traceroute Route Enumeration
⬡
Weakness Classification
▤
Affected Products & Versions
1▤
Affected Packages
1Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
npm
express-handlebars
HIGH
fixed in 5.3.1
⚠
Public Exploits & PoCs
9These PoC and exploit links come from public sources and are not verified to be safe or functional. Review the code before running anything, and treat unverified entries as untrusted.
▣
Scoring & Timeline
8.6
HIGH · CVSS v3.1 · [email protected]
Attack Vector
Network
Adjacent
Local
Physical
Attack Complexity
Low
High
Privileges Required
None
Low
High
User Interaction
None
Required
Scope
Unchanged
Changed
Confidentiality
None
Low
High
Integrity
None
Low
High
Availability
None
Low
High
🔗
References & Sources
3Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/express-handlebars/express-handlebars/blob/78c47a235c4ad7bc2674bddd8ec2721567ed8c72/README.md#danger-Third Party Advisory
https://github.com/express-handlebars/express-handlebars/commit/78c47a235c4ad7bc2674bddd8ec2721567ed8c72PatchThird Party Advisory
https://www.npmjs.com/package/express-handlebarsThird Party Advisory