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CVE-2026-86253

MEDIUMCVSS 5.9/10EPSS 0.43%

Last modified

CVE-2026-86253 is a medium-severity vulnerability rated 5.9/10 on the CVSS scale. h3 (npm package) versions <= 2.0.1-rc.14 contain a path traversal vulnerability in serveStatic(). On Node.js deployments, event.url.pathname is not normalized, so percent-encoded dot segments (%2e%2e) are passed to decodeURI() and decoded to ../ sequences without sanitization. EPSS estimates a 0.43% chance of exploitation in the next 30 days.

Description

h3 (npm package) versions <= 2.0.1-rc.14 contain a path traversal vulnerability in serveStatic(). On Node.js deployments, event.url.pathname is not normalized, so percent-encoded dot segments (%2e%2e) are passed to decodeURI() and decoded to ../ sequences without sanitization. An unauthenticated remote attacker can send crafted requests to endpoints served by serveStatic() to read arbitrary files outside the intended static directory. Fixed in 1.15.6 and 2.0.1-rc.15.

Metrics

CVSS 3.1
5.9/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS 4.0
8.2/10

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability
0.43%

36.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
h3jsh3< 1.15.6; >= 2.0.0-beta.0, < 2.0.1-rc.15

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-86253?
h3 (npm package) versions <= 2.0.1-rc.14 contain a path traversal vulnerability in serveStatic(). On Node.js deployments, event.url.pathname is not normalized, so percent-encoded dot segments (%2e%2e) are passed to decodeURI() and decoded to ../ sequences without sanitization. An unauthenticated remote attacker can send crafted requests to endpoints served by serveStatic() to read arbitrary files outside the intended static directory. Fixed in 1.15.6 and 2.0.1-rc.15.
How severe is CVE-2026-86253?
CVE-2026-86253 has a CVSS score of 5.9/10 (MEDIUM severity). The EPSS model estimates a 0.43% probability of exploitation in the next 30 days.
How do I fix CVE-2026-86253?
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.

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Source: NVD / NIST