CVE-2025-3757Network attack vector

Unauthenticated SSH access via crafted JWS

Published May 13, 2025 · Updated May 13, 2025

Authentication bypass in OpenPubkey SSH 0.9.0 and earlier allows remote attackers to gain SSH access with a specially crafted JWS. The upstream advisory does not disclose which JWS verification routine accepts the crafted signature or the incorrect operation it performs. Exploitation requires an SSH server configured to use opkssh for PK Token verification, where acceptance authorizes the requested connection.

CVSS severity9.3
Critical
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in OpenPubkey SSH 0.9.0 and earlier allows remote attackers to gain SSH access with a specially crafted JWS. The upstream advisory does not disclose which JWS verification routine accepts the crafted signature or the incorrect operation it performs. Exploitation requires an SSH server configured to use opkssh for PK Token verification, where acceptance authorizes the requested connection.

The record

CVE
CVE-2025-3757
Published
May 13, 2025
Updated
May 13, 2025
Vendor
OpenPubkey
Product
OpenPubkey SSH (opkssh)
Classifications
CWE-347, CWE-305, T1078
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2025CVE publishedPublication date reported by the CVE source.
  2. May 13, 2025Record 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=Openpubkey <=0.9.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenPubkey · OpenPubkey SSH (opkssh)version=Openpubkey <=0.9.0

Published CVSS scores

9.3Cloudflare, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:L
9.8NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature
CWE-305Authentication Bypass by Primary Weakness
T1078Valid Accounts

Public exploit references

No public exploit references are available in this record.

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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