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CVE Record

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.50...

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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

A malicious TLS server could crash vulnerable Go-based clients during an RSA key exchange by presenting a certificate whose public-key type does not match what Go expects. The known impact is denial of service for the client process, not data theft or server takeover, based on the provided sources.

Executive priority

Address during normal security patch cycles, with higher priority for Go-based clients that contact untrusted TLS servers. The impact is service disruption rather than confirmed compromise, and the provided sources do not show active exploitation.

Technical view

Go crypto/tls through 1.16.5 failed to assert that an X.509 certificate public key type matched the expected type during RSA-based key exchange. A hostile TLS server could trigger a panic in a TLS client. Distribution and vendor advisories reference updates for affected Go packages.

Likely exposure

Exposure is most likely in applications or appliances built with Go through 1.16.5 that initiate TLS client connections, especially to untrusted or attacker-controlled servers. The bundle does not identify specific vulnerable product versions beyond Go and downstream vendor packages.

Exploitation context

The source bundle describes a malicious TLS server causing a TLS client panic. It provides no evidence of active exploitation, and KEV is false. Treat this as a denial-of-service risk where vulnerable clients connect outbound to untrusted TLS endpoints.

Researcher notes

The vulnerable condition is type confusion or missing assertion in certificate public-key handling during RSA-based TLS key exchange. Evidence is limited to advisory descriptions and downstream package notices; no CVSS vector, CWE, exploit status, or complete affected product matrix is provided.

Mitigation direction

  • Upgrade Go-built software according to Go, distribution, or vendor advisories.
  • Prioritize clients that connect to external or user-supplied TLS endpoints.
  • Check Fedora, Gentoo, NetApp, Oracle, and application vendor guidance where applicable.
  • Rebuild internally maintained Go applications with a non-affected Go release.
  • Monitor vendor advisories if product exposure is unclear.

Validation and detection

  • Inventory Go versions used to build applications and appliances.
  • Identify services that use Go crypto/tls for outbound TLS client connections.
  • Review SBOMs, build metadata, and vendor notices for Go through 1.16.5.
  • Confirm packaged Go updates are applied on affected Linux distributions.
  • Validate remediation through normal regression tests, not offensive TLS testing.
Prepared
Confidence
medium
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
17Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.