CVE-2021-33194
golang.org/x/net/html Infinite Loop vulnerability
golang.org/x/net before v0.0.0-20210520170846-37e1c6afe023 allows attackers to cause a denial of service (infinite loop) via crafted ParseFragment input.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
7.5
golang.org/x/net before v0.0.0-20210520170846-37e1c6afe023 allows attackers to cause a denial of service (infinite loop) via crafted ParseFragment input.
- Record
CVE-2021-33194- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - CVSS 2.0
- 5.0 Medium
AV:N/AC:L/Au:N/C:N/I:N/A:P - Weakness
- CWE-835
- Updated
- 2026-11-02
CVE List No score
golang.org/x/net before v0.0.0-20210520170846-37e1c6afe023 allows attackers to cause a denial of service (infinite loop) via crafted ParseFragment input.
- Record
CVE-2021-33194- Updated
- 2026-11-02
EUVDEUVD-2022-3094 No score
golang.org/x/net before v0.0.0-20210520170846-37e1c6afe023 allows attackers to cause a denial of service (infinite loop) via crafted ParseFragment input.
- Record
EUVD-2022-3094- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-83g2-8m93-v3w7
7.5
golang.org/x/net/html Infinite Loop vulnerability
Go through 1.15.12 and 1.16.x through 1.16.4 has a golang.org/x/net/html infinite loop via crafted ParseFragment input.
- Record
GHSA-83g2-8m93-v3w7- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-835
- Updated
- 2026-11-02
OSV
7.5
golang.org/x/net before v0.0.0-20210520170846-37e1c6afe023 allows attackers to cause a denial of service (infinite loop) via crafted ParseFragment input.
- Record
CVE-2021-33194- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVDEBIAN-CVE-2021-33194
7.5
golang.org/x/net before v0.0.0-20210520170846-37e1c6afe023 allows attackers to cause a denial of service (infinite loop) via crafted ParseFragment input.
- Record
DEBIAN-CVE-2021-33194- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
Show 6 moreShow less
OSVGHSA-83g2-8m93-v3w7
7.5
golang.org/x/net/html Infinite Loop vulnerability
Go through 1.15.12 and 1.16.x through 1.16.4 has a golang.org/x/net/html infinite loop via crafted ParseFragment input.
- Record
GHSA-83g2-8m93-v3w7- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-835
- Updated
- 2026-11-02
OSVUBUNTU-CVE-2021-33194
7.5
golang.org/x/net before v0.0.0-20210520170846-37e1c6afe023 allows attackers to cause a denial of service (infinite loop) via crafted ParseFragment input.
- Record
UBUNTU-CVE-2021-33194- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVBIT-golang-2021-33194 No score
golang.org/x/net before v0.0.0-20210520170846-37e1c6afe023 allows attackers to cause a denial of service (infinite loop) via crafted ParseFragment input.
- Record
BIT-golang-2021-33194- Updated
- 2026-11-02
OSVGO-2021-0238 No score
Infinite loop when parsing inputs in golang.org/x/net/html
An attacker can craft an input to ParseFragment that causes it to enter an infinite loop and never return.
- Record
GO-2021-0238- Updated
- 2026-11-02
OSVUSN-8089-2 No score
golang-golang-x-net-dev vulnerabilities
USN-8089-1 fixed vulnerabilities in Go Networking. This update provides the corresponding update to code vendored in golang-golang-x-net-dev.
Original advisory details:
Bahruz Jabiyev, Tommaso Innocenti, Anthony Gavazzi, Steven Sprecher, and Kaan Onarlioglu discovered that servers using Go Networking could hang during shutdown if preempted by a fatal error. An attacker could possibly use this to cause a denial of service. This issue only affected Ubuntu 22.04 LTS. (CVE-2022-27664)
Arpad Ryszka and Jakob Ackermann discovered that a maliciously crafted stream could cause excessive CPU usage in Go Networking's HPACK decoder. An attacker could possibly use this to cause a denial of service. This issue only affected Ubuntu 22.04 LTS. (CVE-2022-41723)
Mohammad Thoriq Aziz discovered that Go Networking did not properly sanitize some text nodes. An attacker could possibly use this to execute arbitrary code. This issue only affected Ubuntu 22.04 LTS. (CVE-2023-3978)
Sean Ng discovered an error in Go Networking's HTML tag handling. An attacker could possibly use this to cause a denial of service. (CVE-2025-22872)
Guido Vranken and Jakub Ciolek discovered that a maliciously crafted HTML document could exhaust system resources on servers using Go Networking. An attacker could possibly use this to cause a denial of service. (CVE-2025-47911)
Guido Vranken discovered that a maliciously crafted HTML document could put servers using Go Networking into an infinite loop. An attacker could possibly use this to cause a denial of service. (CVE-2025-58190)
- Record
USN-8089-2- Updated
- 2026-11-02
OSVUSN-8089-3 No score
adsys, juju-core, lxd vulnerabilities
USN-8089-1 fixed vulnerabilities in Go Networking. This update provides the corresponding update to code vendored in LXD, ADSys, and Juju Core.
Original advisory details:
Bahruz Jabiyev, Tommaso Innocenti, Anthony Gavazzi, Steven Sprecher, and Kaan Onarlioglu discovered that servers using Go Networking could hang during shutdown if preempted by a fatal error. An attacker could possibly use this to cause a denial of service. This issue only affected Ubuntu 22.04 LTS. (CVE-2022-27664)
Arpad Ryszka and Jakob Ackermann discovered that a maliciously crafted stream could cause excessive CPU usage in Go Networking's HPACK decoder. An attacker could possibly use this to cause a denial of service. This issue only affected Ubuntu 22.04 LTS. (CVE-2022-41723)
Mohammad Thoriq Aziz discovered that Go Networking did not properly sanitize some text nodes. An attacker could possibly use this to execute arbitrary code. This issue only affected Ubuntu 22.04 LTS. (CVE-2023-3978)
Sean Ng discovered an error in Go Networking's HTML tag handling. An attacker could possibly use this to cause a denial of service. (CVE-2025-22872)
Guido Vranken and Jakub Ciolek discovered that a maliciously crafted HTML document could exhaust system resources on servers using Go Networking. An attacker could possibly use this to cause a denial of service. (CVE-2025-47911)
Guido Vranken discovered that a maliciously crafted HTML document could put servers using Go Networking into an infinite loop. An attacker could possibly use this to cause a denial of service. (CVE-2025-58190)
- Record
USN-8089-3- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
golang.org/x/netGo |
before 0.0.0-20210520170846-37e1c6afe023 | 0.0.0-20210520170846-37e1c6afe023 |
golangBitnami |
before 1.15.12, 1.16.0 up to 1.16.4 | 1.15.121.16.4 |
golang-golang-x-netDebian:12 |
before 1:0.0+git20210119.5f4716e+dfsg-4 | 1:0.0+git20210119.5f4716e+dfsg-4 |
golang-golang-x-netDebian:13 |
before 1:0.0+git20210119.5f4716e+dfsg-4 | 1:0.0+git20210119.5f4716e+dfsg-4 |
golang-golang-x-netDebian:14 |
before 1:0.0+git20210119.5f4716e+dfsg-4 | 1:0.0+git20210119.5f4716e+dfsg-4 |
lxdUbuntu:Pro:18.04:LTS |
before 3.0.3-0ubuntu1~18.04.2+esm2, plus listed versions 2.18-0ubuntu62.19-0ubuntu12.20-0ubuntu32.20-0ubuntu42.21-0ubuntu1 Show 16 moreShow less2.21-0ubuntu22.21-0ubuntu32.21-0ubuntu43.0.0~beta2-0ubuntu33.0.0~beta3-0ubuntu33.0.0~beta5-0ubuntu23.0.0~beta7-0ubuntu13.0.0-0ubuntu13.0.0-0ubuntu23.0.0-0ubuntu33.0.0-0ubuntu43.0.1-0ubuntu1~18.04.13.0.2-0ubuntu1~18.04.13.0.3-0ubuntu1~18.04.13.0.3-0ubuntu1~18.04.23.0.3-0ubuntu1~18.04.2+esm1 |
3.0.3-0ubuntu1~18.04.2+esm2 |
golang-golang-x-net-devUbuntu:Pro:20.04:LTS |
before 1:0.0+git20190811.74dc4d7+dfsg-1ubuntu0.1~esm2, plus listed versions 1:0.0+git20190811.74dc4d7+dfsg-11:0.0+git20190811.74dc4d7+dfsg-1ubuntu0.1~esm1 |
1:0.0+git20190811.74dc4d7+dfsg-1ubuntu0.1~esm2 |
golang-golang-x-net-devUbuntu:Pro:16.04:LTS |
before 1:0.0+git20160110.4fd4a9f-1ubuntu0.1~esm2, plus listed versions 0.0+git20150226.3d87fd6-30.0+git20151007.b846920+dfsg-11:0.0+git20150817.66f0418-11:0.0+git20160110.4fd4a9f-11:0.0+git20160110.4fd4a9f-1ubuntu0.1~esm1 |
1:0.0+git20160110.4fd4a9f-1ubuntu0.1~esm2 |
golang-golang-x-net-devUbuntu:Pro:18.04:LTS |
before 1:0.0+git20170629.c81e7f2+dfsg-2ubuntu0.1~esm2, plus listed versions 1:0.0+git20170629.c81e7f2+dfsg-1ubuntu11:0.0+git20170629.c81e7f2+dfsg-1ubuntu21:0.0+git20170629.c81e7f2+dfsg-21:0.0+git20170629.c81e7f2+dfsg-2ubuntu0.1~esm1 |
1:0.0+git20170629.c81e7f2+dfsg-2ubuntu0.1~esm2 |
juju-coreUbuntu:Pro:16.04:LTS |
before 2.3.7-0ubuntu0.16.04.1+esm2, plus listed versions 1.24.6-0ubuntu31.25.0-0ubuntu11.25.0-0ubuntu21.25.0-0ubuntu32.0~beta4-0ubuntu2 Show 11 moreShow less2.0~beta6-0ubuntu1.16.04.12.0~beta7-0ubuntu1.16.04.12.0~beta12-0ubuntu1.16.04.12.0~beta15-0ubuntu2.16.04.12.0.0-0ubuntu0.16.04.22.0.2-0ubuntu0.16.04.12.0.2-0ubuntu0.16.04.22.3.1-0ubuntu0.16.04.12.3.2-0ubuntu0.16.04.12.3.7-0ubuntu0.16.04.12.3.7-0ubuntu0.16.04.1+esm1 |
2.3.7-0ubuntu0.16.04.1+esm2 |
lxdUbuntu:Pro:16.04:LTS |
before 2.0.11-0ubuntu1~16.04.4+esm2, plus listed versions 0.20-0ubuntu40.21-0ubuntu30.21-0ubuntu50.22-0ubuntu10.22-0ubuntu2 Show 45 moreShow less0.23-0ubuntu10.23-0ubuntu20.23-0ubuntu30.24-0ubuntu20.24-0ubuntu30.24-0ubuntu40.25-0ubuntu10.26-0ubuntu20.26-0ubuntu30.27-0ubuntu10.27-0ubuntu22.0.0~beta1-0ubuntu32.0.0~beta1-0ubuntu42.0.0~beta2-0ubuntu12.0.0~beta2-0ubuntu22.0.0~beta3-0ubuntu12.0.0~beta3-0ubuntu22.0.0~beta3-0ubuntu32.0.0~beta3-0ubuntu42.0.0~beta4-0ubuntu12.0.0~beta4-0ubuntu22.0.0~beta4-0ubuntu32.0.0~beta4-0ubuntu42.0.0~beta4-0ubuntu52.0.0~beta4-0ubuntu62.0.0~beta4-0ubuntu72.0.0~rc1-0ubuntu12.0.0~rc1-0ubuntu22.0.0~rc1-0ubuntu32.0.0~rc2-0ubuntu22.0.0~rc2-0ubuntu32.0.0~rc3-0ubuntu12.0.0~rc3-0ubuntu22.0.0~rc3-0ubuntu32.0.0~rc3-0ubuntu42.0.0~rc4-0ubuntu12.0.0~rc5-0ubuntu12.0.0~rc6-0ubuntu12.0.0~rc6-0ubuntu22.0.0~rc7-0ubuntu12.0.0~rc7-0ubuntu22.0.0~rc8-0ubuntu12.0.0~rc8-0ubuntu22.0.0~rc8-0ubuntu32.0.0~rc8-0ubuntu5 |
2.0.11-0ubuntu1~16.04.4+esm2 |
adsysUbuntu:Pro:20.04:LTS |
before 0.9.2~20.04.2ubuntu0.1+esm1, plus listed versions 0.8~22.040.9.2~20.040.9.2~20.04.10.9.2~20.04.20.9.2~20.04.2ubuntu0.1 |
0.9.2~20.04.2ubuntu0.1+esm1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-33194 is a high vulnerability (CVSS 7.5) in Golang Go, published May 26, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 7.49%, the 94th percentile. Fixed in golang.org/x/net 0.0.0-20210520170846-37e1c6afe023.
References
groups.google.com/g/golang-announce/c/wPunbCPkWUg
github.com/golang/net/commit/37e1c6afe02340126705deced573a85ab75209d7
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4CHKSFMHZVOBCZSSVRE3UEYNKARTBMTM
nvd.nist.gov/vuln/detail/CVE-2021-33194
go.dev/cl/311090
go.dev/issue/46288
Show 16 moreShow less
go.googlesource.com/net/+/37e1c6afe02340126705deced573a85ab75209d7
pkg.go.dev/vuln/GO-2021-0238
lists.fedoraproject.org/archives/list/[email protected]/message/4CHKSFMHZVOBCZSSVRE3UEYNKARTBMTM
github.com/advisories/GHSA-83g2-8m93-v3w7
security-tracker.debian.org/tracker/CVE-2021-33194
ubuntu.com/security/CVE-2021-33194
groups.google.com/g/golang-dev/c/28x0nthP-c8/m/KqWVTjsnBAAJ
cve.org/CVERecord?id=CVE-2021-33194
ubuntu.com/security/notices/USN-8089-2
ubuntu.com/security/notices/USN-8089-3
ubuntu.com/security/CVE-2022-27664
ubuntu.com/security/CVE-2022-41723
ubuntu.com/security/CVE-2023-3978
ubuntu.com/security/CVE-2025-22872
ubuntu.com/security/CVE-2025-47911
ubuntu.com/security/CVE-2025-58190
Left out here: 24 versions. The JSON record has them.