What is CVE-2026-25684?

CVE-2026-25684 is File Type Control rule bypass. The supplied enrichment data classifies it as Input Validation mapped to CWE-20 Improper Input Validation.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Exploitation is reported, but no independent confirmation is available in the sources we have. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-25684 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

2 public PoC repositories reported; 1 marked weaponized in current dataset. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with web/proxy/WAF logs, application logs, network IDS/IPS where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-25684 using CVSS 4.4, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

mediumInput Validationpublic exploit

CVE-2026-25684

CVE-2026-25684 — File Type Control rule bypass

A file type attribution issue in Zscaler Internet Access File Type Control evaluation rules may allow improper evaluation of File Type Control policies in rare circumstances.

Published Sep 18, 2026Updated Sep 18, 2026Sources: NVD, Zscaler (CNA), GitHub, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Reported

not confirmed by CISA

EPSS

ahead of 0% of scored CVEs

Affects

Zscaler

ZIA File Type Control

CVSS base

4.4

medium

Remediation

The vendor's own words where we have them.

Upgrade ZIA File Type Control to a fixed release (0 to < 6.2r (current)). Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
Zscaler	ZIA File Type Control	0 to < 6.2r (current)	Patched

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Availability

None

Confidentiality

Low

Integrity

Low

Scope

Changed

Attack Complexity

High

Attack Vector

Network

Privileges Req

Low

User Interaction

Required

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
4.4	CVSS 3.1	medium	1.3	2.7	zscaler.com (CNA), Zscaler (CNA)

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

What this weakness leads to

MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.

MITRE

CWE-20 · Improper Input Validation

DoS: Crash, Exit, or Restart
DoS: Resource Consumption (CPU)
DoS: Resource Consumption (Memory)
Read Memory

Mitigation: Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build recognizers for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses. [REF-1109] [REF-1110] [REF-1111]

Weakness & attack patterns

CWE-20Improper Input Validation

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

CAPEC-67 · String Format Overflow in syslog()CAPEC-261 · Fuzzing for garnering other adjacent user/sensitive dataCAPEC-182 · Flash InjectionCAPEC-267 · Leverage Alternate EncodingCAPEC-71 · Using Unicode Encoding to Bypass Validation LogicCAPEC-46 · Overflow Variables and TagsCAPEC-83 · XPath InjectionCAPEC-22 · Exploiting Trust in ClientCAPEC-3 · Using Leading 'Ghost' Character Sequences to Bypass Input FiltersCAPEC-13 · Subverting Environment Variable ValuesCAPEC-8 · Buffer Overflow in an API CallCAPEC-250 · XML Injection

T1562.003Impair Defenses: Impair Command History Logging
T1574.006Hijack Execution Flow: Dynamic Linker Hijacking
T1574.007Hijack Execution Flow: Path Interception by PATH Environment Variable

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

1 of the 2 sampled are weaponized

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Prioritize edge telemetry for network-reachable ZIA File Type Control.
Monitor for scanner or exploit-pattern traffic after 2 public PoC repositories were reported.

web/proxy/WAF logsapplication logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · CVSS 3.1 4.4 (AV:N)
Sep 18, 2026 · NVD
Initial · CVE published
Sep 18, 2026 · NVD
CVE published by MITRE.
Sep 18, 2026 · SOCRadar CTI

References

1 on the record

help.zscaler.com/zia/release-upgrade-summary-2026
Vendor Advisory

Elsewhere on this site

Zscalerevery CVE for this vendor
Input Validationsame class
CWE-20other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-25684 is File Type Control rule bypass, a medium vulnerability affecting ZIA File Type Control from Zscaler. The current evidence does not list it in CISA KEV, and the exploit status is: Exploitation is reported, but no independent confirmation is available in the sources we have. Public exploit evidence is: 2 public PoC repositories reported; 1 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 4.4 describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.