What is CVE-2026-56853?

CVE-2026-56853 is a high-severity vulnerability in Go Standard Library Net/http, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2026-08-13.

How severe is CVE-2026-56853?

High severity. CVSS v3 base score is 7.5 out of 10.

Resource exhaustion in Go Standard Library Net/http

CVE-2026-56853

When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection to see if they contain the HTTP/2 client preface. ReadHeaderTimeout is unexpectedly not being applied when doing this.

Published 2026-08-13 · last modified 2026-09-03.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.006 (44.9th percentile), scored 2026-09-28.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 45th percentile — 44.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000

Affected products

Go Standard Library Net/http — versions 0, 1.26.0-0, 1.27.0-0

Weakness classification (CWE)

CWE-770 — Allocation of Resources Without Limits or Throttling

References

Frequently asked questions

What is CVE-2026-56853?: CVE-2026-56853 is a high-severity vulnerability in Go Standard Library Net/http, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2026-08-13.
How severe is CVE-2026-56853?: High severity. CVSS v3 base score is 7.5 out of 10.