Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessCraft malicious PDF with JS array logic
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DeliveryDeliver PDF via email or web
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ExploitVictim opens file in Foxit
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ExecutionTrigger use-after-free during array processing
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PersistCorrupt heap and hijack control flow
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ImpactExecute code as current user
Vulnerability Assessment
| Weakness |
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Memory lifecycle management
MITRE ATT&CK
2 techniques across 2 tactics: Execution, Privilege Escalation The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | Exploitation requires the victim to open a specially crafted PDF in a vulnerable version of Foxit PDF Editor or Reader, and requires the application's JavaScript execution to be enabled (the flaw is in JavaScript array-object handling). The mandatory user interaction (UI:R) and the need for attacker-controlled heap state to turn the use-after-free into code execution rather than a mere crash are the primary limiting factors; there is no network-service exposure and no privilege prerequisite (PR:N) beyond luring a user to open the file. Disabling PDF JavaScript in Foxit's preferences mitigates the trigger path. |
| Impact | This is a client-side memory-corruption flaw (CWE-416 use-after-free) with a plausible but not established real-world risk. The vendor CVSS is 7.8 with vector AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - the AV:L reflects that exploitation is local in the sense that a user must open a malicious file on their own machine, and UI:R confirms victim interaction (opening/rendering a crafted PDF) is mandatory. There is no EPSS score, no CISA KEV listing, and no public proof-of-concept referenced, so exploitation status is 'no public exploit identified at time of analysis.' The high C:H/I:H/A:H impact is standard for a UAF that can yield arbitrary code execution, but the description itself hedges ('potentially resulting in ... arbitrary code execution'), meaning weaponization is not confirmed. No conflicting signals are present; the vector is internally consistent with a file-parsing/JavaScript-engine bug. Net: a genuine but not urgent patch-priority item - treat as important for endpoints that routinely open untrusted PDFs, not as an actively-exploited emergency. Note only the vendor advisory bulletin URL is provided, with no specific fixed version, so patch details must be verified against Foxit's security bulletin. |
| Exploit ScenarioDerived | An attacker emails or hosts a specially crafted PDF whose embedded JavaScript manipulates array objects to trigger access of a freed object during array processing. When the victim opens the document in a vulnerable Foxit PDF Editor or Reader (with JavaScript enabled), the use-after-free corrupts memory, causing a crash or, with a controlled heap layout, arbitrary code execution in the user's context. No public exploit code is referenced, and successful RCE requires reliable heap grooming. |
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Alert meAnalysisAIv1 – Sep 23, 2026
Use-after-free in Foxit PDF Editor and Foxit PDF Reader (CWE-416) lets a specially crafted PDF trigger memory corruption while the application processes JavaScript array objects, potentially crashing the viewer or achieving arbitrary code execution in the context of the logged-on user. Exploitation is client-side only: the attacker must lure a victim into opening a malicious PDF with JavaScript execution enabled in the product (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H, 7.8), and there is no privilege prerequisite or network-service exposure. No public exploit code and no confirmed active exploitation (CISA KEV) were identified at time of analysis, and no EPSS score was supplied; turning the use-after-free into reliable code execution additionally depends on attacker-controlled heap state, which is the principal limiting factor beyond the mandatory user interaction.
RemediationAI
No vendor-released patch or exact fixed version was identified in the provided data for CVE-2026-91799; the sole reference is Foxit's security bulletin index at https://www.foxit.com/support/security-bulletins.html, which should be consulted to obtain the build number that addresses this JavaScript array use-after-free, after which Foxit PDF Editor and Foxit PDF Reader should be updated to that release or later, with version verification performed after deployment. Because the vulnerable path is JavaScript array-object handling, the most effective compensating control is to disable PDF JavaScript: in Foxit, open File > Preferences > JavaScript and clear 'Enable JavaScript Actions', then restart the application - this removes the trigger path and is consistent with the assessment that disabling PDF JavaScript mitigates the flaw, but it will break scripted/interactive PDF forms, calculations, and validation logic, so it is best combined with an allow-list for a small number of trusted document sources. Additional hardening worth applying while awaiting the fix: enable Protected View or read-only/trusted-mode restrictions so documents from untrusted locations cannot execute active content, disable the Trust Manager's automatic trust of documents from non-approved locations, remove Foxit as the default PDF handler on high-risk endpoints, educate users not to open PDFs from unsolicited email or untrusted web sources (the attack requires user interaction), and run the reader with least privilege so that any successful exploitation cannot escalate to administrative rights. Browser-embedded and plugin-based PDF rendering should also be disabled where possible, since a crash or corruption in the embedded viewer carries the same client-side risk.
Affected VersionsENISA
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Technical ContextAI · show details
The flaw is a use-after-free (CWE-416) inside Foxit's JavaScript engine, specifically in the handling of JavaScript array objects. During array processing, an object that has already been released is dereferenced, so the application reads or writes memory whose ownership has changed; depending on heap layout and attacker grooming, this manifests either as a crash (denial of service) or as a controllable memory-corruption primitive that can be leveraged for code execution. The affected components are Foxit's client PDF readers/editors, identified by the CPEs cpe:2.3:a:foxit_software_inc.:foxit_pdf_editor and cpe:2.3:a:foxit_software_inc.:foxit_pdf_reader, both listed with unconstrained version ranges, so any version prior to the vendor's fixed build is presumed vulnerable. The CVSS vector AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H confirms the local, client-initiated attack model: the malicious content is delivered as a file, no authentication or account privilege is required, scope remains unchanged, and impact to confidentiality, integrity, and availability is high once exploitation succeeds. Because the trigger path is JavaScript array-object handling, disabling JavaScript execution in the product removes the vulnerable code path entirely, and the need to control freed-memory reuse is why real-world weaponization is plausible rather than demonstrated.
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Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Local file-open vector (AV:L) with required user interaction (UI:R) and no privileges; a UAF enabling code execution justifies full C/I/A high impact, matching the vendor vector.
Primary rating from Vendor (Foxit).
CVSS VectorVendor: Foxit
DescriptionCVE.org
A use-after-free vulnerability exists in Foxit PDF Editor/Reader’s handling of JavaScript array objects. A specially crafted PDF may cause the application to access a released object during array processing, potentially resulting in application crashes or arbitrary code execution.
Executive ViewAI
Foxit PDF Editor and Foxit PDF Reader, widely used for document workflows, contain a high-severity memory corruption vulnerability (CVE-2026-91799) that remains unpatched; no vendor-released patch identified at time of analysis. An attacker could exploit this by enticing a user to open a specially crafted PDF, potentially leading to arbitrary code execution and compromise of the user's system and data. With no public exploit identified at time of analysis, the immediate risk is moderate, but the potential organizational impact-including data loss, ransomware, and productivity disruption-warrants urgent mitigation.
Disable JavaScript execution in Foxit PDF Editor and Foxit PDF Reader; apply application isolation or sandboxing; enforce least privilege for users; monitor vendor advisory for patch release.
Threat Intelligence Overview
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Use-after-free vulnerabilities occur when a program continues to access memory through a pointer after that memory has been deallocated.
Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.
Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.
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EUVD-2026-85124
GHSA-r5mq-pm4h-fg98
NVD
CVE.org
EPSS
Vulnrichment
VulDB
Exploit-DB