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Full vulnerability report · 2026
CVE-2026-12339High confidence

Authenticated Arbitrary File Write Vulnerability in multiple devices

TP-Link Systems Inc. · TL-MR6400 v5.3

6.9MediumCVSS 4.0
Recommended action
Scheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Medium, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 0.53% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict local access and enforce least privilege on affected hosts.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs TP-Link Systems Inc. TL-MR6400 v5.3 and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: As exposure requiresRemediation target: Within 365 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-55700

No EUVD known-exploited evidence

A Zip Slip vulnerability in the WebUI ISP Upgrade functionality allows arbitrary file write via a crafted archive containing directory traversal sequences. An authenticated administrator may overwrite arbitrary files on the system.Successful exploitation may allow arbitrary file to be overwritten on the underlying system, affecting system integrity and availability.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
6.9 · CVSS 4.0
Advisory evidence
No linked advisory details stored yet
Recommended actionScheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
01

What, why and how

A Zip Slip vulnerability in the WebUI ISP Upgrade functionality allows arbitrary file write via a crafted archive containing directory traversal sequences. An authenticated administrator may overwrite arbitrary files on the system.Successful exploitation may allow arbitrary file to be overwritten on the underlying system, affecting system integrity and availability.

What

A Zip Slip vulnerability in the WebUI ISP Upgrade functionality allows arbitrary file write via a crafted archive containing directory traversal sequences. An authenticated administrator may overwrite arbitrary files on the system.Successful exploitation may allow arbitrary file to be overwritten on the underlying system, affecting system integrity and availability.

Why

Attacker-controlled path data is not constrained to the intended directory before the application accesses a file.

How

An attacker operating through an adjacent network may attempt exploitation with elevated privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

A Zip Slip vulnerability in the WebUI ISP Upgrade functionality allows arbitrary file write via a crafted archive containing directory traversal sequences. An authenticated administrator may overwrite arbitrary files on the system.Successful exploitation may allow arbitrary file to be overwritten on the underlying system, affecting system integrity and availability.

Why

Attacker-controlled path data is not constrained to the intended directory before the application accesses a file.

How

An attacker operating through an adjacent network may attempt exploitation with elevated privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
an adjacent network → Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Adjacent
Privileges required
High: elevated access is required
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-22 ↗

CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'). The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:4.0/AV:A/AC:L/AT:N/PR:H/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N

Common Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.

AVAdjacentAttack vector: The attacker must be on an adjacent or logically close network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATNoneAttack requirements: No additional deployment or execution condition is required.PRHighPrivileges required: The attacker needs elevated or administrative privileges.UINoneUser interaction: No action by another user is required.VCNoneVulnerable-system confidentiality: No direct loss is represented by this metric.VIHighVulnerable-system integrity: A successful attack can cause a major loss.VALowVulnerable-system availability: A successful attack can cause a limited loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
CWE-22
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-55700Official EUVD mapping

A Zip Slip vulnerability in the WebUI ISP Upgrade functionality allows arbitrary file write via a crafted archive containing directory traversal sequences. An authenticated administrator may overwrite arbitrary files on the system.Successful exploitation may allow arbitrary file to be overwritten on the underlying system, affecting system integrity and availability.

Official EUVD record ↗
Cyber Security Agency of Singapore · English · CSA-SB-20260812Security Bulletin 12 Aug 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 12 Aug 2026, published on 12 August 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Fixed
An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 10 Aug 2026 · Last source change 25 Aug 2026, 23:31 UTC · CWE-22 · Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-55700
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD awaiting enrichment

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Vendor guidanceAuthoritative vendor guidance changed: removed patch: tp-link.com/v3.20; removed patch: tp-link.com/v8; 1 further removals.
    Before
    patch: tp-link.com/v3.20 · patch: tp-link.com/v8 · remediation: tp-link.com/v3.20
    After
    no authoritative guidance recorded
    CNA ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    < (EU)_1.10.0 0.9.1 v0001.0 Build 260613 RC.76099n; < (EU)_1.10.0 0.9.1 v0001.0 Build 260618 RC.40417n; < (EU)_1.3.0 0.9.1 v0001.0 Build 260605 Rel.57870n; < (EU)_1.5.0 0.9.1 v0001.0 Build 260610 Rel.67978n; < (EU)_1.3.0 0.9.1 v0001.0 Build 260720 Rel.59727n; < (EU)_1.3.0 0.9.1 v0001.0 Build 260609 Rel.49957n; < 1.1.0 0.9.1 v0001.0 Build 260609 Rel35479n, Customized Software for South Korea KT; < 1.2.0 0.9.1 v0001.0 Build 260609 Rel.36250n, Customized Software for South Korea Telenor · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    After
    < (EU)_1.10.0 0.9.1 v0001.0 Build 260613 RC.76099n; < (EU)_1.10.0 0.9.1 v0001.0 Build 260618 RC.40417n; < (EU)_1.3.0 0.9.1 v0001.0 Build 260605 Rel.57870n; < (EU)_1.5.0 0.9.1 v0001.0 Build 260610 Rel.67978n; < (EU)_1.3.0 0.9.1 v0001.0 Build 260720 Rel.59727n; < (EU)_1.3.0 0.9.1 v0001.0 Build 260609 Rel.49957n; < 1.1.0 0.9.1 v0001.0 Build 260609 Rel35479n, Customized Software for South Korea KT; < 1.2.0 0.9.1 v0001.0 Build 260609 Rel.36250n, Customized Software for South Korea Telenor · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
  3. Remediation statusRemediation status changed from Patch available to Awaiting fix.
    Before
    Patch available
    After
    Awaiting fix
    CNA ↗
  4. Vendor guidanceAuthoritative vendor guidance changed: added patch: tp-link.com/v3.20; added patch: tp-link.com/v8; 1 further additions.
    Before
    no authoritative guidance recorded
    After
    patch: tp-link.com/v3.20 · patch: tp-link.com/v8 · remediation: tp-link.com/v3.20
    tp-link.com ↗
  5. Affected versionsThe structured affected or fixed version information changed.
    Before
    < (EU)_1.10.0 0.9.1 v0001.0 Build 260613 RC.76099n; < (EU)_1.10.0 0.9.1 v0001.0 Build 260618 RC.40417n; < (EU)_1.3.0 0.9.1 v0001.0 Build 260605 Rel.57870n · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    < (EU)_1.10.0 0.9.1 v0001.0 Build 260613 RC.76099n; < (EU)_1.10.0 0.9.1 v0001.0 Build 260618 RC.40417n; < (EU)_1.3.0 0.9.1 v0001.0 Build 260605 Rel.57870n; < (EU)_1.5.0 0.9.1 v0001.0 Build 260610 Rel.67978n; < (EU)_1.3.0 0.9.1 v0001.0 Build 260720 Rel.59727n; < (EU)_1.3.0 0.9.1 v0001.0 Build 260609 Rel.49957n; < 1.1.0 0.9.1 v0001.0 Build 260609 Rel35479n, Customized Software for South Korea KT; < 1.2.0 0.9.1 v0001.0 Build 260609 Rel.36250n, Customized Software for South Korea Telenor · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CNA ↗
  6. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    tp-link.com ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
ENISA EUVD · EUVD-2026-55700↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-12339 · cve.blacktree.nl