CVE-2026-136767.5HighCWE-436

CVE-2026-13676: fast-uri vulnerable to host confusion via failed IDN canonicalization

fast-uri

Vendor fix available · Affected: fast-uri · Exploitation: unlikely (under 1%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

0.7%probability of exploitation in the next 30 days

53rd percentile

050100

Higher than 53% of scored CVEs

7.5HighCVSS 3.1

LowMediumHighCrit.

DescriptionCVE.org

fast-uri versions 2.3.1 through 3.1.2 and 4.0.0 fail to canonicalize Unicode (IDN) hostnames for HTTP-family URLs. The IDN conversion path calls a helper that does not exist on the global URL constructor, silently leaving the host in its original Unicode form while normalize() and equal() still return values that differ from a WHATWG-compatible URL parser. Applications that use fast-uri to enforce host-based policy (denylists, loopback filtering, redirect validation, outbound proxy routing) before passing the same URL to Node's URL or fetch can be bypassed when the two implementations resolve the same input to different hosts. Patches: upgrade to fast-uri 3.1.3 for the 3.x line or 4.0.1 for the 4.x line. Workarounds: enforce host policy using the same URL parser used for the actual request, or reject non-ASCII hosts before policy checks.

Affected products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

fast-uri · fast-urifrom 4.0.0 before 4.0.1; from 2.3.1 before 3.1.3

On the Atlas

Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.

Open the Atlas

Exploitation: Unlikely (under 1%). EPSS under 1%, or no score yet.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Interpretation Conflict · Input Validation and Logic
Vendor: fast-uri
Published: June 2026
Band: Unlikely (under 1%), June 2026

CoverageNo articles yet

No CyberSIXT article names CVE-2026-13676 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.

References

28 more references are in the CVE record.