dbcve.org
ZendtoApplication · Zend

CVE-2020-8986

CRITICAL · 9.8 CVSS v3.1 Published 2020-03-24
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
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
lib/NSSDropbox.php in ZendTo prior to 5.22-2 Beta failed to properly check for equality when validating the session cookie, allowing an attacker to gain administrative access with a large number of requests.

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 · moderate confidence

lib/NSSDropbox.php in ZendTo prior to 5.22-2 Beta contains a flawed equality check during session cookie validation. An attacker can exploit this by sending numerous requests to bypass authentication and gain administrative access.

MitigationUpgrade to ZendTo 5.22-2 Beta or later, which implements proper secure equality checking for session cookie validation.

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
ZendtoApplication
Affected:= 3.10= 3.11= 3.12= 3.13= 3.20= 3.51= 3.52= 3.53= 3.54= 3.55= 3.56-2= 3.57

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. Identify installed ZendTo version
    Check the version file or the software itself. Look for a version file in the ZendTo installation directory, or check the main application header/footer for the version number.
    Affected if The installed version matches any of: 3.10, 3.11, 3.12, 3.13, 3.20, 3.51, 3.52, 3.53, 3.54, 3.55, 3.56-2, or 3.57.
  2. Locate the vulnerable file
    Verify the presence of lib/NSSDropbox.php in the ZendTo installation directory. This file contains the session cookie validation logic.
    Affected if The file lib/NSSDropbox.php exists in the ZendTo installation.
  3. Examine session cookie validation code
    Inspect the lib/NSSDropbox.php file for the session cookie validation function. Look for comparison operators used when validating session cookies (search for cookie validation or session verification functions).
    Affected if The code uses weak comparison operators (like == or strcmp without strict mode) for session cookie validation instead of secure comparison methods.
  4. Confirm NSSDropbox is enabled
    Check if the NSSDropbox module is active in the ZendTo configuration. This is the module that handles Dropbox-style functionality and uses the vulnerable session cookie validation.
    Affected if The NSSDropbox module is enabled and used for authentication in the ZendTo deployment.

You are affected if your ZendTo version is any of 3.10 through 3.57 and the NSSDropbox authentication module with the flawed session cookie equality check is in use.

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

Upgrade to ZendTo 5.22-2 Beta or later, which implements proper secure equality checking for session cookie validation.

Recommended fix High confidence

5.22-2 Beta or later

  1. Backup your current ZendTo installation and database before proceeding
  2. Download ZendTo version 5.22-2 Beta or later from the official vendor website (zend.to)
  3. Upgrade your existing ZendTo installation to the new version following the vendor's upgrade instructions
  4. After upgrade, verify the lib/NSSDropbox.php file has been updated with the proper session cookie validation
  5. Confirm administrative access now requires correct session cookie validation

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

Fix this in Zendto Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA3.0 h
13.0 hours of engineering $2,300
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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-2020-8986 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