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CVE Record

CVE-2026-82539: TOTOLINK A720R MAC Filtering cstecgi.cgi setMacFilterRules memory corruption

A vulnerability was determined in TOTOLINK A720R 4.1.5cu.630_B20250509. This impacts the function setMacFilterRules of the file cstecgi.cgi of the component MAC Filtering. Executing a manipulation of the argument desc can lead to memory corruption. The attack may be launched remotely. The exploit has been publicly disclosed and may be utilized.

CriticalCVSS 9.4Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

A flaw in one identified TOTOLINK A720R firmware version can corrupt memory when a privileged user submits a crafted MAC-filter description. Because the management function is remotely reachable in some deployments, compromise could seriously affect the router and connected network. Public exploit material exists, but the supplied evidence does not establish active exploitation.

Executive priority

Treat confirmed affected devices as urgent, especially when management is externally reachable. Restrict administrative exposure immediately, inventory the installed firmware, and monitor for suspicious management activity. Track TOTOLINK guidance closely because the supplied sources identify no patched version. Public exploit availability increases urgency, although the required privileged access lowers broad unauthenticated attack likelihood.

Technical view

CVE-2026-82539 affects setMacFilterRules in cstecgi.cgi on TOTOLINK A720R firmware 4.1.5cu.630_B20250509. Manipulating the desc argument can trigger CWE-119 memory corruption. CVSS 4.0 rates it 9.4: network-accessible, low complexity, no interaction, but requiring high privileges. The sources do not establish code execution or identify a fixed release.

Likely exposure

Exposure is limited by the stated high-privilege requirement, but risk rises sharply where the router management interface is reachable from untrusted networks or administrator credentials are compromised. Only TOTOLINK A720R firmware 4.1.5cu.630_B20250509 is confirmed affected by the supplied sources; other models and versions should not be assumed vulnerable.

Exploitation context

A public repository containing exploit material is referenced, and the CVSS vector marks exploit maturity as proof-of-concept. The CVE is not listed as KEV in the supplied bundle, and no cited evidence confirms exploitation in the wild. Remote exploitation reportedly requires high privileges, reducing unauthenticated mass-exploitation risk without eliminating targeted risk.

Researcher notes

The supplied record establishes controllable memory corruption through desc but does not demonstrate the resulting primitive, code execution, persistence, or authentication bypass. Assessments should preserve the distinction between remote reachability and the CVSS high-privilege prerequisite. Vendor remediation status and the scope beyond the named firmware remain unresolved. Public proof-of-concept availability alone is not evidence of attacks in the wild.

Mitigation direction

  • Disable internet-facing remote administration and restrict management access to trusted networks or a VPN.
  • Identify affected A720R devices and prioritize those exposed to untrusted networks.
  • Check TOTOLINK guidance for a confirmed fixed firmware; no fixed version is named in the supplied sources.
  • Rotate administrator credentials if compromise is suspected and enforce unique, strong credentials.
  • Monitor management activity for unexpected MAC-filter changes, failures, crashes, or reboots.

Validation and detection

  • Confirm each device model and exact installed firmware version through its management interface or asset records.
  • Determine whether the management interface is reachable from the internet or untrusted network segments.
  • Review administrative access records for unfamiliar sessions or MAC-filter configuration changes.
  • Check device stability records for unexplained crashes or reboots following management activity.
  • Verify that vendor-confirmed remediation is installed when guidance becomes available.
  • Avoid testing the public exploit against production devices.
Prepared
Confidence
medium
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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cwe · low confidence lookup

CWE-119: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2026-82539 mapping review

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.4 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P

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.

4CVSS vectors
6Timeline events
1ADP providers
7Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: noTechnical Impact: total

CVSS vector scores

4 official scores

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
9.4CVSS 4.0CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P——VulDB
9.1CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H/E:P/RL:X/RC:R2.36VulDB
9.1CVSS 3.0CriticalCVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H/E:P/RL:X/RC:R2.36VulDB
8.3CVSS 2.0HighAV:N/AC:L/Au:M/C:C/I:C/A:C/E:POC/RL:ND/RC:UR6.410VulDB

Vulnerability scoring details

Base CVSS 4.0 score

9.4Critical
CVSS 4.0 vector shape for CVE-2026-82539Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. Source timelineVulDB

    Advisory disclosed

  2. Source timelineVulDB

    VulDB entry created

  3. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  4. CVE publishedCVE Program

    The CVE record was published.

  5. Source timelineVulDB

    VulDB entry last update

  6. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
TOTOLINKA720R4.1.5cu.630_B20250509Listed
Weakness

CWE details

CWE-119

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

CWE-119 · source CWE mapping

CWE mapping pending import

This CVE carries a CWE mapping that will resolve to a full Glexia CWE intelligence page after the official CWE import is complete.

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