CVE-2021-43565 — crypto
HIGHCVE-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
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2021-43565 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
golang.org/x/cryptoReal-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
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | golang.org/x/crypto | all versions | 0.0.0-20211202192323-5770296d904ego get golang.org/x/crypto@v0.0.0-20211202192323-5770296d904e |
Detection & mitigation playbook
Open-source dependencyDetect
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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-43565 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-43565. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
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
Is CVE-2021-43565 in your dependencies?
O3 Security finds CVE-2021-43565 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.