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PHPApplication

CVE-2017-12933

CRITICAL · 9.8 CVSS v3.0 Published 2017-08-18
Fix available
A fix is available. Upgrade to after 5.6.30 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 finish_nested_data function in ext/standard/var_unserializer.re in PHP before 5.6.31, 7.0.x before 7.0.21, and 7.1.x before 7.1.7 is prone to a buffer over-read while unserializing untrusted data. Exploitation of this issue can have an unspecified impact on the integrity of PHP.

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

A buffer over-read vulnerability exists in PHP's var_unserializer (finish_nested_data function in ext/standard/var_unserializer.re) when processing untrusted serialized data. This allows attackers to read beyond buffer boundaries during unserialize operations, potentially leading to information disclosure or memory corruption.

MitigationUpgrade PHP to version 5.6.31, 7.0.21, or 7.1.7 or later. Additionally, avoid using unserialize() on untrusted data; prefer json_decode() or use the allowed_classes option if unserialize is required.

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
PHPApplication
Affected:<= 5.6.30= 7.0.0= 7.0.1= 7.0.2= 7.0.3= 7.0.4= 7.0.5= 7.0.6= 7.0.7= 7.0.8= 7.0.9= 7.0.10

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. Check installed PHP version
    Run `php -v` on the command line or use `phpinfo()` in a script to retrieve the PHP version
    Affected if The version is 5.6.30 or lower, or any version from 7.0.0 through 7.0.10
  2. Identify unserialize usage in code
    Search PHP source files for calls to the unserialize() function, using commands like `grep -r "unserialize(" /path/to/code`
    Affected if The unserialize() function is called in the codebase
  3. Determine if unserialize processes external input
    Review the code paths that call unserialize() and trace whether the data being unserialized originates from user input, HTTP requests, database fields, or other untrusted sources
    Affected if unserialize() is called with data that comes from untrusted sources such as user input, API calls, or external files
  4. Verify allowed_classes option is not used
    Search for unserialize calls that include the optional second parameter (options/allowed_classes), for example `unserialize($data, ['allowed_classes' => false])`
    Affected if unserialize() is called without the allowed_classes parameter on potentially untrusted data

You are affected if your PHP version falls within 5.6.30 or lower, or 7.0.0 through 7.0.10 AND your code uses unserialize() on untrusted data without the allowed_classes protection.

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 5.6.30
Interim mitigation

Upgrade PHP to version 5.6.31, 7.0.21, or 7.1.7 or later. Additionally, avoid using unserialize() on untrusted data; prefer json_decode() or use the allowed_classes option if unserialize is required.

Recommended fix High confidence

PHP 5.6.31+ / 7.0.21+ / 7.1.7+ (upgrade to the latest stable in your current branch)

  1. 1. Check the current PHP version by running 'php -v' or 'phpinfo()'
  2. 2. For PHP 5.6.x users: Upgrade to PHP 5.6.31 or later (preferably the latest 5.6.x stable release)
  3. 3. For PHP 7.0.x users: Upgrade to PHP 7.0.21 or later (preferably the latest 7.0.x stable release)
  4. 4. For PHP 7.1.x users: Upgrade to PHP 7.1.7 or later (preferably the latest 7.1.x stable release)
  5. 5. After upgrading, restart any web server (Apache, Nginx, PHP-FPM) or PHP-FPM service to load the new version
  6. 6. Verify the new version is active with 'php -v'
  7. 7. Test critical PHP applications to ensure functionality is intact
Caveat Minor version upgrades within the same major.minor branch (e.g., 7.0.x to 7.0.21) typically have minimal breaking changes; test critical functionality after upgrade

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

Fix this in PHP Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,080
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,328.

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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-2017-12933 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