LiveActive security incident?Get immediate response
CVE Record

CVE-2026-19812: TOTOLINK A800R product.so cstecgi.cgi UploadCustomModule stack-based overflow

A weakness has been identified in TOTOLINK A800R 4.1.2cu.5137_B20200730. This affects the function UploadCustomModule of the file /cgi-bin/cstecgi.cgi of the component product.so. This manipulation of the argument File causes stack-based buffer overflow. The attack is possible to be carried out remotely. The exploit has been made available to the public and could be used for attacks.

CriticalCVSS 9Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

A flaw in one confirmed TOTOLINK A800R firmware version can overflow memory when its custom-module upload function processes a crafted File value. A remote attacker with required access could potentially take control, alter data, or disrupt the router. Public exploit material exists, increasing urgency, but confirmed active exploitation is not documented.

Executive priority

Treat confirmed affected devices as an immediate remediation priority, especially if administration is internet-accessible. Public exploit material and potentially complete device compromise justify rapid containment. Prioritize inventory, access restriction, vendor verification, and replacement planning if no corrected firmware is available.

Technical view

CVE-2026-19812 is a stack-based buffer overflow in UploadCustomModule within product.so, reached through /cgi-bin/cstecgi.cgi. The affected File argument lacks adequate bounds handling. The supplied CVSS v2 vector indicates network reachability, low complexity, authentication required, and potentially complete confidentiality, integrity, and availability impact.

Likely exposure

Confirmed exposure is limited to TOTOLINK A800R firmware 4.1.2cu.5137_B20200730. Risk is greatest where the management interface is reachable from untrusted networks or credentials are compromised. The bundle does not confirm that other versions are affected.

Exploitation context

A public proof of concept is referenced, so capable attackers can study the flaw. The CVSS vector indicates authentication is required. The supplied data does not show a CISA KEV listing or confirmed attacks in the wild; public availability alone is not evidence of active exploitation.

Researcher notes

The report maps to CWE-119 and CWE-121. Evidence identifies the vulnerable function, endpoint, argument, and exact firmware build, but the supplied CVSS uses version 2 and marks report confidence unconfirmed. No vendor advisory, corrected version, or forensic indicators are established in the bundle.

Mitigation direction

  • Identify A800R devices running the confirmed affected firmware version.
  • Restrict the management interface to trusted administrative networks and users.
  • Disable internet-facing administration where operationally feasible.
  • Check TOTOLINK guidance for a corrected firmware release or vendor-approved mitigation.
  • Consider replacing affected devices if no supported remediation is available.

Validation and detection

  • Confirm each device model and complete firmware build number.
  • Verify whether cstecgi.cgi is reachable from untrusted networks.
  • Review administrative access controls and remove unnecessary accounts.
  • Review logs for unusual custom-module upload activity or unexpected configuration changes.
  • After remediation, confirm the affected firmware is absent and management exposure remains restricted.
Prepared
Confidence
medium
Sources
5

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.

Open ATT&CK lookup
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-2026-19812 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
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-2026-19812Attack 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.