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Debian LinuxOperating system · Debian

CVE-2017-17434

CRITICAL · 9.8 CVSS v3.0 Published 2017-12-06
Fix available
A fix is available. Upgrade to after 3.1.2 or later.
See remediation →
100/100
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
The daemon in rsync 3.1.2, and 3.1.3-development before 2017-12-03, does not check for fnamecmp filenames in the daemon_filter_list data structure (in the recv_files function in receiver.c) and also does not apply the sanitize_paths protection mechanism to pathnames found in "xname follows" strings (in the read_ndx_and_attrs function in rsync.c), which allows remote attackers to bypass intended access restrictions.

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 rsync daemon versions 3.1.2 and 3.1.3-development before 2017-12-03 contains two access restriction bypass vulnerabilities: it fails to validate fnamecmp filenames against the daemon_filter_list, and it does not apply sanitize_paths protection to pathnames in 'xname follows' strings, allowing remote attackers to bypass intended access controls.

MitigationUpgrade rsync to version 3.1.3 or later (or apply the relevant patch), and ensure rsync daemon is not directly exposed to untrusted networks.

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
Debian LinuxOperating system
Affected:= 8.0= 9.0
RsyncApplication
Affected:<= 3.1.2

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

CVSS:3.0/AV:N/AC:L/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. Check rsync installation and version
    Run 'rsync --version' to identify the installed rsync version
    Affected if Version is 3.1.2 or 3.1.3-development (any build date before 2017-12-03)
  2. Determine if rsync daemon is in use
    Check for running rsyncd process with 'ps aux | grep rsync' or review startup scripts for rsyncd daemon mode
    Affected if rsync daemon (rsyncd) is actively running or configured to run
  3. Locate rsync daemon configuration
    Common paths: /etc/rsyncd.conf, /etc/rsync/rsyncd.conf, or check 'man rsyncd.conf' for default locations
    Affected if rsyncd.conf exists and daemon mode is configured
  4. Inspect daemon_filter_list configuration
    Search rsyncd.conf for 'daemon filter' or 'filter' directives within module definitions; these define path access restrictions
    Affected if daemon_filter_list or filter rules are defined in any module
  5. Check xname follows configuration
    Search rsyncd.conf for 'auth users' or 'secrets file' entries that use 'xname follows' syntax
    Affected if Module uses auth users with xname follows strings referencing paths

You are affected if running rsync daemon version 3.1.2 or 3.1.3-development (pre-2017-12-03) with daemon_filter_list or xname follows path configurations, as the vulnerability bypasses these access controls.

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 a release after 3.1.2
Interim mitigation

Upgrade rsync to version 3.1.3 or later (or apply the relevant patch), and ensure rsync daemon is not directly exposed to untrusted networks.

Recommended fix High confidence

rsync 3.1.3 or later (Debian 8: 3.1.1-3+deb8u1, Debian 9: 3.1.2-1+deb9u1)

  1. 1. Identify the installed rsync version by running: rsync --version
  2. 2. For Debian 8 (Jessie): Upgrade rsync to version 3.1.1-3+deb8u1 or later using: apt-get update && apt-get install rsync
  3. 3. For Debian 9 (Stretch): Upgrade rsync to version 3.1.2-1+deb9u1 or later using: apt-get update && apt-get install rsync
  4. 4. For upstream rsync: Upgrade to version 3.1.3 or later from https://rsync.samba.org/
  5. 5. Verify the fix by checking: rsync --version and ensuring the version is >= 3.1.3

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

Fix this in Debian Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing3.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,210
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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-2017-17434 in production — separate from our analysis above.

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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