dbcve.org
FedoraOperating system · Fedoraproject

CVE-2023-25136

MEDIUM · 6.5 CVSS v3.1 Published 2023-02-03
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
74/100
Remediation priority · Elevated
High EPSS Public exploit Remotely reachable No privileges Zero-click Patch available

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 · unedited
OpenSSH server (sshd) 9.1 introduced a double-free vulnerability during options.kex_algorithms handling. This is fixed in OpenSSH 9.2. The double free can be leveraged, by an unauthenticated remote attacker in the default configuration, to jump to any location in the sshd address space. One third-party report states "remote code execution is theoretically possible."

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
How this class of weakness works · CWE-415

The same block of memory is freed twice, corrupting the allocator's bookkeeping in ways an attacker can shape toward code execution. It usually stems from tangled ownership of a pointer. The fix is clear, single ownership of each allocation and clearing pointers once they are freed.

General guidance for the double free class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

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
FedoraOperating system
Affected:= 37= 38
OpensshApplication
Affected:= 9.1
Ontap Select Deploy Administration UtilityApplication
Affected:all versions
A250 FirmwareOperating system
Affected:all versions
500f FirmwareOperating system
Affected:all versions
C250 FirmwareOperating system
Affected:all versions

CVSS 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
None
Integrity
Low
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H

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.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch ftp.openbsd.org →
Recommended fix High confidence

OpenSSH 9.2

  1. Identify the OpenSSH version currently installed using: sshd -V or ssh -V
  2. For Fedora systems: Run 'dnf update openssh' to obtain OpenSSH 9.2 which contains the fix
  3. For other Linux distributions: Use the native package manager to update openssh to version 9.2 or later
  4. For NetApp Ontap Select Deploy: Apply the vendor-supplied firmware update from NetApp support
  5. For NetApp storage systems (A250, 500f, C250): Apply the firmware update from NetApp support that addresses this vulnerability
  6. After updating, verify the new version using: sshd -V
  7. Restart the sshd service to load the fixed version: systemctl restart sshd (or appropriate service manager)
Caveat Upgrading OpenSSH may require updating client configurations if older key exchange algorithms are in use; test in non-production first

Generated from the published advisory — verify against the referenced sources before acting.

We can apply and verify the patch for your build — typical engagement from $1,600. Get the patch applied

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-25136 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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