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CrowdApplication · Atlassian

CVE-2016-6496

CRITICAL · 9.8 CVSS v3.0 Published 2016-12-09
Fix available
A fix is available. Upgrade to after 2.8.4 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 LDAP directory connector in Atlassian Crowd before 2.8.8 and 2.9.x before 2.9.5 allows remote attackers to execute arbitrary code via an LDAP attribute with a crafted serialized Java object, aka LDAP entry poisoning.

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

Atlassian Crowd's LDAP directory connector deserializes LDAP attribute values without proper validation. Attackers with write access to LDAP directories can poison LDAP entries with malicious serialized Java objects, which Crowd will deserialize during directory synchronization, leading to arbitrary code execution.

MitigationUpgrade Atlassian Crowd to version 2.8.8 or 2.9.5 and later to patch the deserialization vulnerability. As a compensating control, restrict LDAP directory write permissions to trusted administrators only.

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
CrowdApplication
Affected:<= 2.8.4= 2.9.0= 2.9.1

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. Identify installed Crowd version
    Access the Crowd admin console and navigate to /admin/footer.jspa or check thecrowd-install/atlassian-user.xml file for the version number
    Affected if Version is 2.8.4 or earlier, 2.9.0, or 2.9.1
  2. Confirm LDAP directory connector is configured
    In Crowd admin console, go to Users > Directory Server to verify an LDAP directory is connected
    Affected if An LDAP directory connector is actively configured and syncing
  3. Check if directory synchronization is enabled
    Review the LDAP directory configuration to confirm 'Synchronize' is enabled or check scheduled sync jobs in the administration panel
    Affected if Directory synchronization is turned on (manual or scheduled)
  4. Assess LDAP write access controls
    Review the permissions on the LDAP directory to determine if untrusted users have write access to LDAP attributes
    Affected if Users other than trusted administrators can write to LDAP directory entries

You are affected if Atlassian Crowd with an active LDAP connector is running version 2.8.4 or earlier, 2.9.0, or 2.9.1 and the LDAP directory allows write access to untrusted users.

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 2.8.4
Interim mitigation

Upgrade Atlassian Crowd to version 2.8.8 or 2.9.5 and later to patch the deserialization vulnerability. As a compensating control, restrict LDAP directory write permissions to trusted administrators only.

Recommended fix High confidence

Crowd 2.8.8 (for 2.8.x branch) or Crowd 2.9.5 (for 2.9.x branch)

  1. 1. Identify the currently installed Crowd version by checking the application UI or configuration files
  2. 2. Determine which upgrade path applies: if running 2.8.x (2.8.4 or earlier), upgrade to 2.8.8; if running 2.9.x (2.9.0-2.9.4), upgrade to 2.9.5
  3. 3. Back up the Crowd home directory and database before performing the upgrade
  4. 4. Download the appropriate fixed version of Atlassian Crowd from the official Atlassian download server
  5. 5. Review the Crowd upgrade guide and release notes for pre-upgrade checklist items
  6. 6. Stop the Crowd service
  7. 7. Run the installer or deploy the new version following Atlassian's standard upgrade procedure
  8. 8. Start the Crowd service and verify the application is operational
Caveat Check Atlassian release notes for each intermediate version between your current version and the target version for any breaking changes or required migration steps

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

Fix this in Crowd Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.

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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-2016-6496 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