Public proof of conceptFix available

CVE-2021-34558

Q: Is CVE-2021-34558 actively exploited?

Active exploitation of CVE-2021-34558 has not been confirmed. Its EPSS score was 7.0% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-34558?

CVE-2021-34558 has a CVSS v3 base score of 6.5 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

A public proof of concept exists; no exploitation attested.

Published2021-07-15
Fixed in1.16.6 · 1.15.14
WeaknessCWE-295

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC

2021-07-1514:15CVE publishedNVD
2026-10-2319:23First public proof of conceptPoC-in-GitHub

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-34558?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-34558?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV

Branch	Affected	Fixed in	Source
1.16	≥ 1.16.0, < 1.16.6	1.16.6	NVD · OSV
1.16	≥ 1.16.0-0, < 1.16.6	1.16.6	OSV
1.15	< 1.15.14	1.15.14	NVD · OSV

Fedoraproject fedora

Branch	Affected	Fixed in	Source
33.x	= 33	no fix published	NVD
34.x	= 34	no fix published	NVD

Netapp cloud insights telegraf

Branch	Affected	Fixed in	Source
—	all versions	no fix published	NVD

3 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

grafanaAlmaLinux:8all versions · fixed in 7.5.9-4.el8
podmanAlmaLinux:9all versions · fixed in 2:4.2.0-3.el9and 5 other packages

Vendor advisories

RHSA-2022:1372 Red Hat Product Security72 products fixed
Red Hat Security Advisory: Red Hat OpenShift Data Foundation 4.10.0 enhancement, security & bug fix update

Full record on NVD

Fix

Update Go to 1.16.6 · 1.15.14
Vendor fix Red Hat Product Security RHSA-2022:1372 · 72 productsFor details on how to apply this update, refer to: https://access.redhat.com/articles/11258
Workaround from the vendor Red Hat Product Security RHSA-2022:1372 · 72 productsMitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Advisories and patches

golang.orgRelease Notes · Vendor Advisory
groups.google.comRelease Notes
www.oracle.comPatch
www.oracle.comPatch

Detection

read 2026-10-23 19:23 UTC

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: 1 repository, unverifiedalexzorin/cve-2021-34558

Sources

NVDCVSS 3.16.5read 2026-10-23
NVDCVSS 2.02.6read 2026-10-23
NVDweakness (CWE)CWE-295read 2026-10-23
FIRST EPSSEPSS score7.0 %2026-10-22
PoC-in-GitHubproof of concept1read 2026-10-23
OSVaffected packages—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Published: 2021-07-15
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-34558?

Is CVE-2021-34558 actively exploited?

Active exploitation of CVE-2021-34558 has not been confirmed. Its EPSS score was 7.0% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-34558?

CVE-2021-34558 has a CVSS v3 base score of 6.5 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

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