CVE-2021-37634

MEDIUM
Published Aug 9, 20214y ago · Modified Jun 17, 20262w ago
6.1 CVSS 3.1
Medium
Find Similar
Published Aug 9, 2021 4y ago
Last Modified Jun 17, 2026 2w ago

Description

Leafkit is a templating language with Swift-inspired syntax. Versions prior to 1.3.0 are susceptible to Cross-site Scripting (XSS) attacks. This affects anyone passing unsanitised data to Leaf's variable tags. Before this fix, Leaf would not escape any strings passed to tags as variables. If an attacker managed to find a variable that was rendered with their unsanitised data, they could inject scripts into a generated Leaf page, which could enable XSS attacks if other mitigations such as a Content Security Policy were not enabled. This has been patched in 1.3.0. As a workaround sanitize any untrusted input before passing it to Leaf and enable a CSP to block inline script and CSS data.

CVSS Details

Base Score
6.1
Exploitability
2.8
Impact
2.7
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction Required
Scope Changed
Confidentiality Low
Integrity Low
Availability None

Threat Intelligence

No active exploitation signals — not in CISA KEV and no EPSS score yet.

Exploit & Patch Status
No Known Exploit
No Patch Available

Weaknesses 1

CWE-79 Cross-site Scripting Injection

Affected Products 1

VendorProductVersionRange
vaporleafkit* <1.3.0

References 2

  • github.com https://github.com/vapor/leaf-kit-ghsa-rv3x-xq3r-8j9h/pull/1
    Broken Link
  • github.com https://github.com/vapor/leaf-kit/security/advisories/GHSA-rv3x-xq3r-8j9h
    Third Party Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.