CVE-2021-33194: golang.org/x/net/html Infinite Loop vulnerability

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 7.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-05-26 · updated 2026-06-17
Weakness: CWE-835

Description

golang.org/x/net before v0.0.0-20210520170846-37e1c6afe023 allows attackers to cause a denial of service (infinite loop) via crafted ParseFragment input.

Affected products

Fedoraproject Fedora: 36
Go: through 1.15.12; from 1.16.0 through 1.16.4
Golang.Org/X/Net: before 0.0.0-20210520170846-37e1c6afe023 — fixed in 0.0.0-20210520170846-37e1c6afe023

How to fix

Upgrade to a fixed version: Golang.Org/X/Net 0.0.0-20210520170846-37e1c6afe023. Check the vendor advisory for mitigations.

References

https://github.com/golang/net/commit/37e1c6afe02340126705deced573a85ab75209d7
https://groups.google.com/g/golang-announce/c/wPunbCPkWUg
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4CHKSFMHZVOBCZSSVRE3UEYNKARTBMTM/
https://github.com/golang/net/commit/37e1c6afe02340126705deced573a85ab75209d7
https://groups.google.com/g/golang-announce/c/wPunbCPkWUg
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4CHKSFMHZVOBCZSSVRE3UEYNKARTBMTM/

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