What is CVE-2021-27918?

CVE-2021-27918 is a high-severity vulnerability in Golang Go, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 7.5/10. Published 2021-03-11.

How severe is CVE-2021-27918?

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

Is CVE-2021-27918 known to be exploited?

6 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Golang Go

CVE-2021-27918

encoding/xml in Go before 1.15.9 and 1.16.x before 1.16.1 has an infinite loop if a custom TokenReader (for xml.NewTokenDecoder) returns EOF in the middle of an element. This can occur in the Decode, DecodeElement, or Skip method.

Published 2021-03-11 · last modified 2026-06-17.

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: 0.025 (83.9th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 84th percentile — 83.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.025 · newest: 0.025 · change: 0.000

Affected products

Golang Go

Weakness classification (CWE)

CWE-835 — Loop with Unreachable Exit Condition (Infinite Loop)

Public proof-of-concept exploits

References

groups.google.com/g/golang-announce/c/MfiLYjG-RAw (Mailing List, Third Party Advisory)
security.gentoo.org/glsa/202208-02 (vendor-advisory, Third Party Advisory)

Frequently asked questions

What is CVE-2021-27918?: CVE-2021-27918 is a high-severity vulnerability in Golang Go, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 7.5/10. Published 2021-03-11.
How severe is CVE-2021-27918?: High severity. CVSS v3 base score is 7.5 out of 10.
Is CVE-2021-27918 known to be exploited?: 6 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.