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FedoraOperating system · Fedoraproject

CVE-2016-3125

HIGH · 7.5 CVSS v3.0 Published 2016-04-05
Fix available
A fix is available. Upgrade to after 1.3.5 or later.
See remediation →
84/100
Remediation priority · High
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
The mod_tls module in ProFTPD before 1.3.5b and 1.3.6 before 1.3.6rc2 does not properly handle the TLSDHParamFile directive, which might cause a weaker than intended Diffie-Hellman (DH) key to be used and consequently allow attackers to have unspecified impact via unknown vectors.

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

The mod_tls module in ProFTPD fails to properly process the TLSDHParamFile directive, causing the server to fall back to weaker Diffie-Hellman parameters instead of using the configured (presumably stronger) DH keys. This weakens the TLS key exchange and could allow attackers to perform cryptographic attacks against FTP sessions.

MitigationUpdate ProFTPD to version 1.3.5b or 1.3.6rc2 or later, and verify that TLSDHParamFile points to a strong DH parameter file (minimum 2048-bit recommended).

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
FedoraOperating system
Affected:= 22= 23
ProftpdApplication
Affected:<= 1.3.5= 1.3.6
OpensuseOperating system
Affected:= 13.1

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
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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 checks

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

  1. Check ProFTPD version
    Run `proftpd -v` or check package version with `rpm -q proftpd` (Fedora/openSUSE) or `dpkg -l proftpd` (Debian-based)
    Affected if Version is 1.3.5 or earlier, or exactly 1.3.6, on Fedora 22/23, openSUSE 13.1, or similar distributions
  2. Verify mod_tls module is loaded
    Check for `LoadModule mod_tls.c` in proftpd.conf (typically in /etc/proftpd/ or /etc/) or run `proftpd -l` to list compiled-in modules
    Affected if mod_tls is loaded and TLS is enabled for FTP connections
  3. Locate TLSDHParamFile directive
    Search proftpd.conf for `TLSDHParamFile` directive: `grep -r TLSDHParamFile /etc/proftpd/` or check the main configuration file
    Affected if TLSDHParamFile is configured but may not be applied due to the bug
  4. Inspect configured DH parameter file
    If TLSDHParamFile is set, examine the referenced file (e.g., `cat /etc/ssl/certs/dhparams.pem`) and check the key size - the bug causes ProFTPD to ignore this and use weak built-in 512-bit or 1024-bit DH parameters
    Affected if The file contains strong DH parameters (2048-bit or higher) but the server still uses weak DH due to the bug
  5. Check for TLS cipher configuration
    Look for `TLSCipherSuite` or `TLSProtocol` directives in proftpd.conf to see if weak ciphers or older protocols are allowed
    Affected if Configuration allows export-grade or weak ciphers that could be exploited once the DH weakness is present

If running ProFTPD 1.3.5 or 1.3.6 with mod_tls enabled and TLSDHParamFile configured, the server is likely using weak Diffie-Hellman parameters despite the configuration pointing to stronger ones.

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.

From vendor data
Upgrade available Upgrade to a release after 1.3.5
Interim mitigation

Update ProFTPD to version 1.3.5b or 1.3.6rc2 or later, and verify that TLSDHParamFile points to a strong DH parameter file (minimum 2048-bit recommended).

Fix this in Fedora Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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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-2016-3125 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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