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Ubuntu LinuxOperating system · Canonical

CVE-2017-16548

CRITICAL · 9.8 CVSS v3.1 Published 2017-11-06
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 receive_xattr function in xattrs.c in rsync 3.1.2 and 3.1.3-development does not check for a trailing '\0' character in an xattr name, which allows remote attackers to cause a denial of service (heap-based buffer over-read and application crash) or possibly have unspecified other impact by sending crafted data to the daemon.

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 heap-based buffer over-read vulnerability exists in rsync's receive_xattr function (xattrs.c) in versions 3.1.2 and 3.1.3-development. The function fails to validate the presence of a trailing null terminator ('\0') in extended attribute names, allowing remote attackers sending crafted data to the rsync daemon to read beyond heap buffer boundaries. This can cause denial of service via application crash and potentially enable arbitrary code execution.

MitigationUpdate rsync to version 3.1.3-stable or later, which includes the null terminator check. If immediate patching is not possible, restrict or disable daemon mode access and consider blocking external xattr-handling connections at the network perimeter.

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
Ubuntu LinuxOperating system
Affected:= 12.04= 14.04= 16.04= 17.10
Debian LinuxOperating system
Affected:= 7.0= 8.0= 9.0
RsyncApplication
Affected:> 2.6.9, <= 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:3.1/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 version
    Run 'rsync --version' and note the version number in the output (e.g., rsync version 3.1.2)
    Affected if Version is 3.1.2 or 3.1.3-development (versions prior to 3.1.3-stable)
  2. Identify if rsync daemon is running
    Check for running rsyncd process with 'ps aux | grep rsyncd' or look for /etc/rsyncd.conf configuration file
    Affected if rsync daemon mode is actively running or configured to run
  3. Verify daemon configuration for xattr support
    Inspect /etc/rsyncd.conf for any share definitions; check if the system uses extended attributes (xattrs) in any rsync transfer configurations
    Affected if rsyncd is configured and daemon mode accepts incoming connections that could include xattr data
  4. Confirm daemon exposure
    Review network listening status with 'netstat -tlnp | grep 873' or 'ss -tlnp | grep 873' to see if rsync daemon port 873 is listening
    Affected if rsync daemon port 873 is open and accessible on network interfaces

Affected if rsync version is 3.1.2 or 3.1.3-development AND the rsync daemon is enabled and exposed, allowing remote attackers to send crafted xattr data.

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

Update rsync to version 3.1.3-stable or later, which includes the null terminator check. If immediate patching is not possible, restrict or disable daemon mode access and consider blocking external xattr-handling connections at the network perimeter.

Recommended fix High confidence

rsync 3.1.3 or later

  1. Check current rsync version by running: rsync --version
  2. For Ubuntu/Debian systems, update package lists: sudo apt-get update
  3. Upgrade rsync to the fixed version: sudo apt-get install rsync
  4. Verify the upgraded version: rsync --version
  5. If running rsync as a daemon, restart the service: sudo systemctl restart rsync

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

Fix this in Ubuntu Linux Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
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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-2017-16548 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