CVE-2026-93600Network attack vector

Certificate acceptance via ignored URI name constraints

Published Sep 18, 2026 · Updated Sep 21, 2026

Improper certificate validation in Rustls rustls-webpki allows attackers to bypass X.509 URI name constraints in affected releases. The X.509 name-constraints path ignores URI-name constraints and accepts the certificate chain instead of rejecting that unsupported constraint. Exploitation requires successful signature verification and a misissued certificate in versions 0.101.0 through 0.103.11 or 0.104.0-alpha.1 through 0.104.0-alpha.5; the library exposes no API for asserting URI names.

CVSS severity2.1
Low
EPSS probability0.18%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in Rustls rustls-webpki allows attackers to bypass X.509 URI name constraints in affected releases. The X.509 name-constraints path ignores URI-name constraints and accepts the certificate chain instead of rejecting that unsupported constraint. Exploitation requires successful signature verification and a misissued certificate in versions 0.101.0 through 0.103.11 or 0.104.0-alpha.1 through 0.104.0-alpha.5; the library exposes no API for asserting URI names.

The record

CVE
CVE-2026-93600
Published
Sep 18, 2026
Updated
Sep 21, 2026
Vendor
Rustls
Product
rustls-webpki
Classifications
CWE-295
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Sep 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.101.0 <0.103.12
  2. Affected versionversion=0.104.0-alpha.1 <0.104.0-alpha.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Rustls · rustls-webpkiversion=0.101.0 <0.103.12; version=0.104.0-alpha.1 <0.104.0-alpha.6

Published CVSS scores

2.1VulnCheck CNACVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
2.2GitHub Security AdvisoryCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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