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CVE Record

CVE-2026-19813: TOTOLINK A800R firewall.so cstecgi.cgi setMacFilterRules stack-based overflow

A security vulnerability has been detected in TOTOLINK A800R 4.1.2cu.5137_B20200730. This impacts the function setMacFilterRules of the file /cgi-bin/cstecgi.cgi of the component firewall.so. Such manipulation of the argument Comment leads to stack-based buffer overflow. The attack may be performed from remote. The exploit has been disclosed publicly and may be used.

CriticalCVSS 9Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

A remotely reachable flaw in one listed TOTOLINK A800R firmware version can corrupt device memory when an authenticated user submits an oversized MAC-filter comment. The published score indicates possible loss of confidentiality, integrity, and availability. Public proof-of-concept material exists, but the sources do not establish active exploitation or identify a vendor patch.

Executive priority

Urgent. Locate affected routers promptly and remove untrusted management exposure. Public proof-of-concept availability and potential full security impact justify rapid containment, although authenticated access is reportedly required and active exploitation is unconfirmed. Escalate replacement planning if TOTOLINK provides no verified patch.

Technical view

CVE-2026-19813 is a stack-based buffer overflow in firewall.so's setMacFilterRules function, reached through /cgi-bin/cstecgi.cgi. Improper handling of the Comment argument affects A800R firmware 4.1.2cu.5137_B20200730. The supplied CVSS v2 vector is 9.0, network-accessible with low complexity and required authentication. Consequences beyond memory corruption are not demonstrated in the bundle.

Likely exposure

Confirmed scope is limited to TOTOLINK A800R firmware 4.1.2cu.5137_B20200730. Risk is highest where the management CGI is reachable by untrusted or compromised authenticated users, especially through WAN exposure. The bundle does not confirm other firmware versions, default exposure, or required account privilege.

Exploitation context

Proof-of-concept material has been publicly disclosed, increasing practical risk. However, the CVSS vector indicates authentication is required, CISA KEV status is false, and no supplied source confirms exploitation in the wild. Treat public disclosure as elevated opportunity, not evidence of active attacks.

Researcher notes

The evidence identifies CWE-119 and CWE-121 and a vulnerable Comment parameter, but does not establish reliable code execution, affected adjacent versions, authentication privilege, or vendor remediation. The listed CPE contains a wildcard firmware version while the affected record names one build; do not infer broader impact without testing or vendor confirmation.

Mitigation direction

  • Identify and prioritize A800R devices running the listed firmware.
  • Restrict management access to trusted administrative networks and authorized users.
  • Disable WAN-facing management where operationally possible.
  • Review TOTOLINK guidance for patched firmware or supported replacement options.
  • Replace or isolate affected devices if no verified remediation is available.

Validation and detection

  • Inventory A800R hardware and record each installed firmware version.
  • Verify whether /cgi-bin/cstecgi.cgi is reachable from untrusted networks.
  • Review administrative accounts and remove unnecessary or compromised access.
  • Check TOTOLINK guidance for firmware addressing CVE-2026-19813.
  • Monitor device and gateway logs for unusual authenticated configuration requests.
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

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

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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cwe · low confidence lookup

CWE-121: 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.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-19813 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
Critical
CVSS
9 (2.0)
Known Exploited
No
Published

Vector: AV:N/AC:L/Au:S/C:C/I:C/A:C/E:POC/RL:ND/RC:UR

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
9CVSS 2.0CriticalAV:N/AC:L/Au:S/C:C/I:C/A:C/E:POC/RL:ND/RC:UR810VulDB
8.8CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:X/RC:R2.85.9VulDB
8.8CVSS 3.0HighCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:X/RC:R2.85.9VulDB
8.7CVSS 4.0HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P——VulDB

Vulnerability scoring details

Base CVSS 4.0 score

8.7High
CVSS 4.0 vector shape for CVE-2026-19813Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/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. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  3. Source timelineVulDB

    VulDB entry created

  4. Source timelineVulDB

    VulDB entry last update

  5. CVE publishedCVE Program

    The CVE record was published.

  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
TOTOLINKA800R4.1.2cu.5137_B20200730Listed
Weakness

CWE details

CWE-119CWE-121

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