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Debian LinuxOperating system · Debian

CVE-2016-9774

HIGH · 7.8 CVSS v3.0 Published 2017-03-23
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
80/100
Remediation priority · High
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 postinst script in the tomcat6 package before 6.0.45+dfsg-1~deb7u4 on Debian wheezy, before 6.0.35-1ubuntu3.9 on Ubuntu 12.04 LTS and on Ubuntu 14.04 LTS; the tomcat7 package before 7.0.28-4+deb7u8 on Debian wheezy, before 7.0.56-3+deb8u6 on Debian jessie, before 7.0.52-1ubuntu0.8 on Ubuntu 14.04 LTS, and on Ubuntu 12.04 LTS, 16.04 LTS, and 16.10; and the tomcat8 package before 8.0.14-1+deb8u5 on Debian jessie, before 8.0.32-1ubuntu1.3 on Ubuntu 16.04 LTS, before 8.0.37-1ubuntu0.1 on Ubuntu 16.10, and before 8.0.38-2ubuntu1 on Ubuntu 17.04 might allow local users with access to the tomcat account to obtain sensitive information or gain root privileges via a symlink attack on the Catalina localhost directory.

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 postinst script in multiple Debian and Ubuntu Tomcat packages (6, 7, and 8) contains a symlink attack vulnerability in the Catalina localhost directory handling. Local users with access to the tomcat account can exploit this to read sensitive files or escalate privileges to root by creating malicious symlinks during or after package installation.

MitigationUpgrade to the patched Tomcat package versions (tomcat6 6.0.45+dfsg-1~deb7u4+, tomcat7 7.0.28-4+deb7u8+/7.0.56-3+deb8u6+, tomcat8 8.0.14-1+deb8u5+/8.0.32-1ubuntu1.3+). Alternatively, audit existing Catalina localhost directory permissions and remove any suspicious 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
Affected:= 7.0= 8.0
Ubuntu LinuxOperating system
Affected:= 12.04= 14.04= 16.04= 16.10
TomcatWeb server / proxy
Affected:= 6.0= 7.0= 8.0

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
High
Availability
High

CVSS:3.0/AV:L/AC:L/PR:L/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. Identify installed Tomcat package version
    Run 'dpkg -l | grep tomcat' (Debian/Ubuntu) or check /usr/share/tomcat*/etc/tomcat*.json or /etc/tomcat* tomcat-version files
    Affected if The installed version matches the vulnerable releases: tomcat6 versions before 6.0.45+dfsg-1~deb7u4, tomcat7 versions before 7.0.28-4+deb7u8 (Debian 7) or 7.0.56-3+deb8u6 (Debian 8) or 7.0.72-1ubuntu1.3 (Ubuntu), tomcat8 versions before 8.0.14-1+deb8u5 (Debian 8) or 8.0.32-1ubuntu1.3 (Ubuntu)
  2. Locate the Catalina localhost directory
    Find the Catalina base (typically /var/lib/tomcat*/ or /var/lib/tomcat*) and check for the 'conf/Catalina/localhost' directory
    Affected if The Catalina localhost directory exists and is writable by the tomcat user or tomcat group, allowing symlink creation
  3. Inspect for suspicious symlinks in localhost directory
    Run 'ls -la <catalina_base>/conf/Catalina/localhost/' and look for symlinks pointing outside the webapp directories or to sensitive system files
    Affected if Any symlinks exist in the localhost directory that point to locations outside the expected webapp deployment area, especially to /etc/, /root/, or other sensitive directories
  4. Check ownership and permissions on Catalina directories
    Run 'ls -la <catalina_base>/conf/Catalina/' and verify the owner and permissions on the localhost subdirectory
    Affected if The tomcat user or any unprivileged local user has write access to create symlinks in the Catalina localhost directory
  5. Audit recent file creation in Catalina directory
    Run 'find <catalina_base>/conf/Catalina/ -type l -mtime -30' (or adjust timeframe) to find recently created symlinks
    Affected if Symlinks were created recently in the Catalina directory, indicating potential exploitation activity

A system is affected if it runs a vulnerable Tomcat package version (pre-patch) AND the tomcat user or local attackers have write access to the Catalina localhost directory where malicious symlinks could be created.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to the patched Tomcat package versions (tomcat6 6.0.45+dfsg-1~deb7u4+, tomcat7 7.0.28-4+deb7u8+/7.0.56-3+deb8u6+, tomcat8 8.0.14-1+deb8u5+/8.0.32-1ubuntu1.3+). Alternatively, audit existing Catalina localhost directory permissions and remove any suspicious symlinks.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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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-2016-9774 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
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  • Version or environment caveats, and links to real fixes
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