Debian LinuxOperating system · Debian
CVE-2017-9525
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 · uneditedIn the cron package through 3.0pl1-128 on Debian, and through 3.0pl1-128ubuntu2 on Ubuntu, the postinst maintainer script allows for group-crontab-to-root privilege escalation via symlink attacks against unsafe usage of the chown and chmod programs.
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 confidenceThe cron package's postinst maintainer script uses chown and chmod unsafely, creating symlink attack vectors that allow users with group-crontab access to escalate privileges to root by manipulating file ownership and permissions through malicious symlinks.
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
= 8.0= 9.0<= 3.0pl1-128.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
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:H/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 checksWork through these to decide whether this CVE applies to you.
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Verify cron package is installedRun: dpkg -l | grep cron (Debian) or rpm -q cron (RPM-based)Affected if cron package is not installed means not affected
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Determine installed cron versionRun: dpkg -l cron 2>/dev/null | grep ^ii or rpm -qi cron 2>/dev/nullAffected if Version is 3.0pl1-128 or lower on Debian, or <= 3.0pl1-128 on upstream Cron Project, indicates vulnerable version
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Locate the postinst maintainer scriptFind the postinst file: dpkg -L cron | grep postinst or search for /var/lib/dpkg/info/cron.postinstAffected if Script exists and has not been patched for safe file operations
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Inspect postinst for unsafe chown/chmod usageExamine the postinst file content: cat /var/lib/dpkg/info/cron.postinst and look for chown/chmod commands without symlink safety checks (such as -h flag or target verification)Affected if The script contains chown or chmod commands operating on user-controlled paths without symlink protection (no -h flag, no existence checks before operation)
You are affected if cron version is 3.0pl1-128 or earlier AND the postinst maintainer script contains unsafe chown/chmod operations that do not protect against symlink attacks.
Generated from the published advisory. Verify against your own configuration.
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 dataApply the patched cron package version (post 3.0pl1-128 on Debian, post 3.0pl1-128ubuntu2 on Ubuntu) or manually patch the postinst maintainer script to use safe file operation practices that verify symlink targets before chown/chmod.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-9525 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2017-9525 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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