dbcve.org
PppApplication · Canonical

CVE-2020-15704

MEDIUM · 5.5 CVSS v3.1 Published 2020-09-01
Fix available
A fix is available. Upgrade to 2.4.5-5ubuntu1.4 / 2.4.5-5.1ubuntu2.3 or later.
See remediation →
57/100
Remediation priority · Elevated
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 modprobe child process in the ./debian/patches/load_ppp_generic_if_needed patch file incorrectly handled module loading. A local non-root attacker could exploit the MODPROBE_OPTIONS environment variable to read arbitrary root files. Fixed in 2.4.5-5ubuntu1.4, 2.4.5-5.1ubuntu2.3+esm2, 2.4.7-1+2ubuntu1.16.04.3, 2.4.7-2+2ubuntu1.3, 2.4.7-2+4.1ubuntu5.1, 2.4.7-2+4.1ubuntu6. Was ZDI-CAN-11504.

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 vulnerability in the modprobe child process within the load_ppp_generic_if_needed patch file allows local non-root attackers to exploit the MODPROBE_OPTIONS environment variable to read arbitrary root-owned files. The flaw stems from improper handling of module loading where user-controlled environment variables are passed to the modprobe process.

MitigationApply the appropriate fixed package versions (2.4.5-5ubuntu1.4, 2.4.5-5.1ubuntu2.3+esm2, 2.4.7-1+2ubuntu1.16.04.3, 2.4.7-2+2ubuntu1.3, 2.4.7-2+4.1ubuntu5.1, or 2.4.7-2+4.1ubuntu6) for the affected PPP daemon package. Consider restricting MODPROBE_OPTIONS in privileged contexts until patching is complete.

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
PppApplication
Affected:< 2.4.7-1\+ubuntu1.16.04.3< 2.4.7-2\+2ubuntu1.3< 2.4.7-2\+4.1ubuntu5.1< 2.4.5-5ubuntu1.4< 2.4.5-5.1ubuntu2.3\+esm2

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

CVSS:3.1/AV:L/AC:L/PR:L/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. Verify PPP package is installed
    Run 'dpkg -l ppp' or 'apt list --installed | grep ppp' to check if the ppp package is present on the system
    Affected if The ppp package is not installed on the system
  2. Check installed PPP version
    Run 'dpkg -s ppp' and note the Version field, then compare against the affected ranges: < 2.4.7-1+ubuntu1.16.04.3, < 2.4.7-2+2ubuntu1.3, < 2.4.7-2+4.1ubuntu5.1, < 2.4.5-5ubuntu1.4, or < 2.4.5-5.1ubuntu2.3+esm2
    Affected if The installed version is lower than any of the fixed version thresholds listed
  3. Identify MODPROBE_OPTIONS usage in PPP context
    Run 'strings /usr/sbin/pppd | grep -i modprobe' or examine the pppd binary for references to MODPROBE_OPTIONS environment variable being passed to modprobe child processes
    Affected if The pppd binary uses MODPROBE_OPTIONS from the environment when spawning modprobe child processes
  4. Check for vulnerable load_ppp_generic_if_needed code
    If source is available, examine the load_ppp_generic_if_needed function in the PPP source code to confirm it passes environment variables (specifically MODPROBE_OPTIONS) to the modprobe subprocess without sanitization
    Affected if The code passes unsanitized environment variables to the modprobe process
  5. Test for local exploitation feasibility
    As a non-root user, attempt to set MODPROBE_OPTIONS to point to a root-owned file and trigger PPP module loading (e.g., by initiating a PPP connection) to verify if arbitrary file read is possible
    Affected if A non-root user can read root-owned files through MODPROBE_OPTIONS manipulation when PPP triggers module loading

A system is affected if it runs a PPP package version lower than the fixed thresholds AND the pppd binary passes MODPROBE_OPTIONS environment variable to modprobe child processes, allowing local non-root users to read arbitrary root-owned files.

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 2.4.5-5ubuntu1.4 / 2.4.5-5.1ubuntu2.3 / 2.4.7-1 or later
Fixed in 2.4.5-5ubuntu1.42.4.5-5.1ubuntu2.32.4.7-1
Interim mitigation

Apply the appropriate fixed package versions (2.4.5-5ubuntu1.4, 2.4.5-5.1ubuntu2.3+esm2, 2.4.7-1+2ubuntu1.16.04.3, 2.4.7-2+2ubuntu1.3, 2.4.7-2+4.1ubuntu5.1, or 2.4.7-2+4.1ubuntu6) for the affected PPP daemon package. Consider restricting MODPROBE_OPTIONS in privileged contexts until patching is complete.

Fix this in Ppp Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,224.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2020-15704 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2020-15704 in production — separate from our analysis above.

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.

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