How severe is CVE-2021-43565?

CVE-2021-43565 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-43565?

CVE-2021-43565 affects the following packages: golang.org/x/crypto (Go). Ecosystems affected: Go.

How do I fix CVE-2021-43565?

Update golang.org/x/crypto to 0.0.0-20211202192323-5770296d904e or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-43565 is resolved across your whole dependency graph.

How do I detect CVE-2021-43565 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for golang.org/x/crypto, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-43565 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2021-43565 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-43565 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-43565?

CVE-2021-43565 has an EPSS (Exploit Prediction Scoring System) score of 1.2%, placing it in the 68th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was CVE-2021-43565 published, and has it been updated?

CVE-2021-43565 was published on September 6, 2022 and was last updated on June 24, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

HIGH severity

CVE-2021-43565 — x/crypto

HIGH

CVE-2021-43565 is a high-severity (CVSS 7.5) vulnerability in golang.org/x/crypto. A fix is available for golang.org/x/crypto — see the affected versions and patch details below.

x/crypto/ssh vulnerable to panic via malformed packets

Also known asGHSA-gwc9-m7rh-j2wwGO-2022-0968

Published

Sep 6, 2022

Updated

Jun 24, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.2%probability of exploitation in next 30 days

Lower Risk+0.20%

Lower risk than most CVEs68th percentile — riskier than 68% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

🐹golang.org/x/crypto

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

The x/crypto/ssh package before 0.0.0-20211202192323-5770296d904e of golang.org/x/crypto allows an unauthenticated attacker to panic an SSH server. When using AES-GCM or ChaCha20Poly1305, consuming a malformed packet which contains an empty plaintext causes a panic.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`golang.org/x/crypto`	all versions	0.0.0-20211202192323-5770296d904e`go get golang.org/x/crypto@v0.0.0-20211202192323-5770296d904e`

Affected Products

1 product · 1 configurations

Application

sshgolang

< 0.0.0-20211202192323-5770296d904e

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for golang.org/x/crypto, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update golang.org/x/crypto to 0.0.0-20211202192323-5770296d904e or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-43565 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

go-toolset shipped with Red Hat Developer Tools - Compilers and golang shipped with Red Hat Enterprise Linux 8 are not affected by this flaw because they do not ship the vulnerable code. This flaw was rated to have a Moderate impact because it is not shipped in the Golang standard library and thus has a reduced impact…

Product	Fixed in	Advisory
OpenShift Service Mesh 2.0	`kiali-0:v1.24.7.redhat1-1.el8`	RHSA-2022:1276
Red Hat OpenShift Container Platform 4.11	`cri-o-0:1.24.1-11.rhaos4.11.gitb0d2ef3.el8`	RHSA-2022:5068
Red Hat OpenShift Container Platform 4.11	`openshift4/ose-installer:v4.11.0-202208020235.p0.g3768430.assembly.stream`	RHSA-2022:5069
Red Hat OpenShift Data Foundation 4.10 on RHEL8	`mcg-0:5.10.0-72.el8`	RHSA-2022:1361
Red Hat OpenShift Data Foundation 4.10 on RHEL8	`odf4/cephcsi-rhel8:v4.10.0-35`	RHSA-2022:1372
Red Hat OpenStack Platform 16.2	`rhosp-rhel8-tech-preview/osp-director-operator:1.2.3-3`	RHSA-2022:5673
RHACS-3.69-RHEL-8	`advanced-cluster-security/rhacs-main-rhel8:3.69.2-5`	RHSA-2022:5188
RHEL-8 based Middleware Containers	`amq7/amq-broker-rhel8-operator:7.12.0-16`	RHSA-2024:2944

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2021-43565 in your dependencies?

Find it across Go, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

7.5/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Weaponization

No Nuclei template, Metasploit module or public proof-of-concept found.

Timeline

Disclosed

Sep 6, 2022

Last updated

Jun 24, 2026

Identifiers

CVE-2021-43565

GHSA-gwc9-m7rh-j2ww

GO-2022-0968

References

Advisorynvd.nist.gov · CVE 2021 43565 Reportgroups.google.com · 2AR1sKiM Qs Webgroups.google.com · forum Webgo.dev Webgo.dev Webgroups.google.com · forum Webpkg.go.dev · GO 2022 0968

Related vulnerabilities

This CVE is high severity; 5 of 8 other CVEs affecting crypto are rated as high or higher (top: critical).

CVE-2026-39828CVE-2026-42508CVE-2026-39835CVE-2026-39831CVE-2026-46598CVE-2026-39832CVE-2026-39833CVE-2026-46597

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedJun 24, 2026

CVE-2021-43565 — x/crypto

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Fixing This On Your OS

Frequently Asked Questions

Is CVE-2021-43565 in your dependencies?