CVE-2026-86231Public exploitNetwork attack vector

Host authentication bypass via dropped revocation entries

Published Sep 6, 2026 · Updated Sep 6, 2026

Certificate revocation bypass in mwiede JSch 2.28.0 through 2.28.5 allows remote attackers to have revoked SSH host certificates accepted. KnownHosts parses certificate-form @revoked entries as unknown, drops their marker and type binding, and getRevokedKeys excludes them from the revocation set. Exploitation requires OpenSSH certificate-based host authentication and a certificate-type token in the @revoked entry; the revoked server identity is then trusted.

CVSS severity6.3
Medium
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Certificate revocation bypass in mwiede JSch 2.28.0 through 2.28.5 allows remote attackers to have revoked SSH host certificates accepted. KnownHosts parses certificate-form @revoked entries as unknown, drops their marker and type binding, and getRevokedKeys excludes them from the revocation set. Exploitation requires OpenSSH certificate-based host authentication and a certificate-type token in the @revoked entry; the revoked server identity is then trusted.

The record

CVE
CVE-2026-86231
Published
Sep 6, 2026
Updated
Sep 6, 2026
Vendor
mwiede
Product
JSch
Classifications
CWE-298, CWE-299, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 6, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 6, 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=2.28.0
  2. Affected versionversion=2.28.1
  3. Affected versionversion=2.28.2
  4. Affected versionversion=2.28.3
  5. Affected versionversion=2.28.4
  6. Affected versionversion=2.28.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

mwiede · JSchversion=2.28.0; version=2.28.1; version=2.28.2; version=2.28.3; version=2.28.4; version=2.28.5

Published CVSS scores

3.7TenableCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
2.6TenableAV:N/AC:H/Au:N/C:N/I:P/A:N
6.3TenableCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
2.9OSVCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P

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.

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

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-298Improper Validation of Certificate Expiration
CWE-299Improper Check for Certificate Revocation
T1557Adversary-in-the-Middle

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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