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LibsshApplication

CVE-2025-5987

HIGH · 8.1 CVSS v3.1 Published 2025-07-07
Fix available
A fix is available. Upgrade to 0.11.2 or later.
See remediation →
90/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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
A flaw was found in libssh when using the ChaCha20 cipher with the OpenSSL library. If an attacker manages to exhaust the heap space, this error is not detected and may lead to libssh using a partially initialized cipher context. This occurs because the OpenSSL error code returned aliases with the SSH_OK code, resulting in libssh not properly detecting the error returned by the OpenSSL library. This issue can lead to undefined behavior, including compromised data confidentiality and integrity or crashes.

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 · high confidence

A flaw in libssh's ChaCha20 cipher implementation with OpenSSL causes heap exhaustion errors to go undetected because the OpenSSL error code aliases with SSH_OK. This results in libssh using a partially initialized cipher context, leading to undefined behavior including compromised data confidentiality/integrity or crashes.

MitigationUpdate to patched libssh version when available; avoid using ChaCha20 cipher with OpenSSL until patched; implement proper memory management to reduce heap exhaustion risk.

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
LibsshApplication
Affected:>= 0.10.0, < 0.11.2

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
High
Integrity
High
Availability
High

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

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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed libssh version
    Run 'ssh -V' or check your system's package manager for libssh version, or inspect libssh shared library file version
    Affected if version is 0.10.0 or higher but lower than 0.11.2
  2. Determine libssh crypto backend
    Check which crypto library libssh is linked against by examining linked libraries (ldd on the ssh binary or libssh.so), or review build configuration
    Affected if libssh is linked against OpenSSL (libssl) as the cryptographic backend
  3. Identify ChaCha20 cipher usage
    Review SSH server/client configuration files for any configured ciphers, or capture SSH session negotiation and examine the cipher list proposed/accepted
    Affected if ChaCha20 cipher is enabled or negotiated in SSH connections

You are affected if libssh version is between 0.10.0 and 0.11.1 (inclusive), uses OpenSSL as the crypto backend, and ChaCha20 cipher is in use or enabled.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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
Upgrade available Upgrade to 0.11.2 or later
Fixed in 0.11.2
Interim mitigation

Update to patched libssh version when available; avoid using ChaCha20 cipher with OpenSSL until patched; implement proper memory management to reduce heap exhaustion risk.

Recommended fix High confidence

libssh 0.11.2 or later

  1. Check current libssh version installed (e.g., `rpm -q libssh` or `dpkg -l | grep libssh`)
  2. Upgrade to libssh version 0.11.2 or later using your distribution's package manager (e.g., `yum update libssh` or `apt-get install libssh0.11`)
  3. Rebuild or restart any applications or services that depend on libssh to ensure they use the updated library
  4. Verify the fix by confirming the installed version is >= 0.11.2
Caveat Minimal risk - this is a bugfix release addressing a security flaw; however, test critical functionality after upgrade to ensure compatibility

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

Fix this in Libssh Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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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-2025-5987 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
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