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CVE Record

CVE-2013-3735: The Zend Engine in PHP before 5.4.16 RC1, and 5.5.0 before RC2, does not properly determine whether a parse...

The Zend Engine in PHP before 5.4.16 RC1, and 5.5.0 before RC2, does not properly determine whether a parser error occurred, which allows context-dependent attackers to cause a denial of service (memory consumption and application crash) via a crafted function definition, as demonstrated by an attack within a shared web-hosting environment. NOTE: the vendor's http://php.net/security-note.php page says "for critical security situations you should be using OS-level security by running multiple web servers each as their own user id.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Older PHP Zend Engine versions can crash or consume excessive memory when parsing a specially crafted function definition. The main business risk is service outage, especially where untrusted users can upload or run PHP code, such as shared hosting. The source bundle does not show data theft, integrity impact, or active exploitation.

Executive priority

Prioritize if the organization still operates legacy PHP or shared-hosting services. The impact is outage rather than confidentiality loss, but the low-complexity availability risk makes unsupported exposed systems a business continuity concern.

Technical view

CVE-2013-3735 is a parser-error handling flaw in PHP before 5.4.16 RC1 and PHP 5.5.0 before RC2. A crafted function definition can cause denial of service through memory consumption and application crash. The supplied CVSS 3.1 vector is availability-only: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Likely exposure

Exposure is likely limited to legacy PHP deployments older than 5.4.16 RC1 or 5.5.0 RC2. Risk is highest in shared web-hosting or platforms where untrusted tenants can introduce PHP code. Modern maintained PHP versions should not be affected based on the supplied version bounds.

Exploitation context

The source bundle describes context-dependent attackers and a shared web-hosting demonstration. KEV is false, and no cited source in the bundle states active exploitation. Treat this as a denial-of-service risk, not evidence of remote code execution or data compromise.

Researcher notes

The evidence points to parser error state handling in Zend Engine, with remediation reflected in PHP source and release notes. Affected product metadata in the bundle is sparse, so validation should rely on deployed PHP versions and distribution backport documentation.

Mitigation direction

  • Upgrade PHP beyond 5.4.16 RC1 or 5.5.0 RC2 where applicable.
  • Check current PHP vendor or OS distribution guidance for supported fixed packages.
  • Avoid shared execution contexts for untrusted PHP tenants.
  • Use OS-level isolation with separate web server users for critical separation.
  • Retire unsupported PHP 5.x environments where replacement is feasible.

Validation and detection

  • Inventory externally reachable and shared-hosting PHP runtimes.
  • Confirm PHP versions are not before 5.4.16 RC1 or 5.5.0 RC2.
  • Review hosting models for untrusted tenant PHP execution.
  • Check crash or memory-exhaustion logs on legacy PHP hosts.
  • Verify vendor package changelogs include the relevant PHP fix.
Prepared
Confidence
high
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2013-3735 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2013-3735Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.