CVE-2021-34558: The crypto/tls package of Go through 1.16.5 does not properly assert that the type of public key in an X.509 c

Q: How do I fix CVE-2021-34558?

go: upgrade to 1.15.14, 1.16.6; fedora: mitigate or apply the listed mitigation; cloud insights telegraf: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-34558 being exploited?

CVE-2021-34558 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-34558 affect?

CVE-2021-34558 affects go, fedora, cloud insights telegraf. Severity is medium (CVSS 6.5). The crypto/tls package of Go through 1.16.5 does not properly assert that the type of public key in an X.509 certificate matches the expected type when doing a RSA based key exchange, allowing a malicious TLS server to cause a TLS client to

Q: How urgent is CVE-2021-34558?

Priority 46/100. EPSS top 6%: very likely to be exploited

This month

MEDIUM 6.5UPGRADEMITIGATEMITIGATE

CVE-2021-34558 is a medium-severity flaw (CVSS 6.5) affecting go, fedora, cloud insights telegraf. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The crypto/tls package of Go through 1.16.5 does not properly assert that the type of public key in an X.509 certificate matches the expected type when doing a RSA based key exchange, allowing a malicious TLS server to cause a TLS client to panic.

Why this priority

EPSS top 6%: very likely to be exploited

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	7.0% (top 6%)
CISA exploited list	No
Weakness	CWE-295
Published	2021-07-15
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fedoraproject · golang · netapp · oracle

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-07-15 14:15 UTCPublished CVE record published
2026-06-17 03:56 UTCUpdated Record last modified

golang go UPGRADE

Affected: < 1.15.14 · >= 1.16.0 and < 1.16.6

Fixed in: 1.15.14, 1.16.6

Safe to downgrade to: a release before 1.16.0

1. Check installed version

apt-cache policy go || rpm -q go || go --version

2. UPGRADE to 1.15.14 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade go

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade go

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 1.16.0 (Debian / Ubuntu)

apt-cache madison go sudo apt install go=<VERSION_BEFORE_1.16.0> sudo apt-mark hold go

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list go sudo dnf downgrade go-<VERSION_BEFORE_1.16.0> sudo dnf versionlock add go

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

fedoraproject fedora MITIGATE

Affected: 33 · 34

Fixed in: no fixed release known

Safe to downgrade to: a release before 33

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

netapp cloud insights telegraf MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy cloud-insights-telegraf || rpm -q cloud-insights-telegraf || cloud-insights-telegraf --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

netapp storagegrid MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy storagegrid || rpm -q storagegrid || storagegrid --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

netapp trident MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy trident || rpm -q trident || trident --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

oracle timesten in-memory database UPGRADE

Affected: < 21.1.1.1.0

Fixed in: 21.1.1.1.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy timesten-in-memory-database || rpm -q timesten-in-memory-database || timesten-in-memory-database --version

2. UPGRADE to 21.1.1.1.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade timesten-in-memory-database

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade timesten-in-memory-database

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-34558?

go: upgrade to 1.15.14, 1.16.6; fedora: mitigate or apply the listed mitigation; cloud insights telegraf: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-34558 being exploited?

CVE-2021-34558 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-34558 affect?

CVE-2021-34558 affects go, fedora, cloud insights telegraf. Severity is medium (CVSS 6.5). The crypto/tls package of Go through 1.16.5 does not properly assert that the type of public key in an X.509 certificate matches the expected type when doing a RSA based key exchange, allowing a malicious TLS server to cause a TLS client to

How urgent is CVE-2021-34558?

Priority 46/100. EPSS top 6%: very likely to be exploited

Software pages

Go (Golang) vulnerabilities

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References

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