What is CVE-2026-49859?

CVE-2026-49859 is a medium-severity vulnerability in Denoland Deno, classified under Protection Mechanism Failure. CVSS score: 5.2/10. Published 2026-06-23.

How severe is CVE-2026-49859?

Medium severity. CVSS v3 base score is 5.2 out of 10.

SSRF in Denoland Deno

CVE-2026-49859

Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, when fetch() was called, Deno checked the destination hostname against --deny-net rules but did not re-check the IP addresses that hostname resolved to. An attacker…

CVSS v3 metric

CVSS v3 base score 5.2 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N.

Affected products

Denoland Deno — versions < 2.8.1

Weakness classification (CWE)

CWE-693 — Protection Mechanism Failure
CWE-918 — Server-Side Request Forgery (SSRF)

References

security-advisories@github.com (x_refsource_CONFIRM)

Frequently asked questions

What is CVE-2026-49859?: CVE-2026-49859 is a medium-severity vulnerability in Denoland Deno, classified under Protection Mechanism Failure. CVSS score: 5.2/10. Published 2026-06-23.
How severe is CVE-2026-49859?: Medium severity. CVSS v3 base score is 5.2 out of 10.