CVE-2026-35387
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedOpenSSH before 10.3 can use unintended ECDSA algorithms. Listing of any ECDSA algorithm in PubkeyAcceptedAlgorithms or HostbasedAcceptedAlgorithms is misinterpreted to mean all ECDSA algorithms.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceIn OpenSSH before 10.3, there is a logic flaw in how ECDSA algorithms are handled in PubkeyAcceptedAlgorithms and HostbasedAcceptedAlgorithms configuration directives. When a user lists even a single ECDSA algorithm (such as ecdsa-sha2-nistp256), the SSH server misinterprets this as a directive to accept ALL ECDSA algorithms, including potentially weaker or unintended variants. This bypasses the user's explicit algorithm restrictions and could allow authentication with ECDSA key types the administrator did not intend to permit.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 10.3CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
-
Check installed OpenSSH versionRun 'sshd -v' or 'ssh -V' to display the version number, or check the package manager for openssh versionAffected if Version is before 10.3 (e.g., 10.2, 10.1, etc.)
-
Examine PubkeyAcceptedAlgorithms in sshd_configRead /etc/ssh/sshd_config and locate the PubkeyAcceptedAlgorithms directive. If commented out, the default appliesAffected if The directive contains any ECDSA algorithm (ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, ecdsa-sha2-nistp512) and especially if ONLY ECDSA algorithms are listed
-
Examine HostbasedAcceptedAlgorithms in sshd_configRead /etc/ssh/sshd_config and locate the HostbasedAcceptedAlgorithms directive. If commented out, the default appliesAffected if The directive contains any ECDSA algorithm and especially if ONLY ECDSA algorithms are listed
-
Check for default algorithm behaviorIf both PubkeyAcceptedAlgorithms and HostbasedAcceptedAlgorithms are commented out (using defaults), defaults may include all ECDSA algorithms which could be affectedAffected if Using defaults with ECDSA host keys and running OpenSSH < 10.3
User is affected if running OpenSSH version before 10.3 AND has any ECDSA algorithm listed in PubkeyAcceptedAlgorithms or HostbasedAcceptedAlgorithms, as a single listed ECDSA algorithm is misinterpreted as enabling all ECDSA algorithms.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data10.3
Review and audit PubkeyAcceptedAlgorithms and HostbasedAcceptedAlgorithms configurations to avoid partial ECDSA algorithm listings; upgrade to OpenSSH 10.3 when available, or explicitly specify exact algorithm lists to avoid unintended all-ECDSA matching behavior.
- Consultation2.0 h
- Implementation1.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,696.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-35387 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-35387 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data