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CVE-2021-37634

MEDIUMCVSS 6.1/10EPSS 0.71%

Last modified

CVE-2021-37634 is a medium-severity vulnerability rated 6.1/10 on the CVSS scale. Leafkit is a templating language with Swift-inspired syntax. Versions prior to 1.3.0 are susceptible to Cross-site Scripting (XSS) attacks. EPSS estimates a 0.71% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
6.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS Probability
0.71%

48.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
VaporLeafkit< 1.3.0

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2021-37634?
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.
How severe is CVE-2021-37634?
CVE-2021-37634 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 0.71% probability of exploitation in the next 30 days.
How do I fix CVE-2021-37634?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-37634?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST