Security readout for executives and security teams
Plain-English summary
A flaw in one identified TOTOLINK A800R firmware version allows an authenticated remote user to trigger a memory corruption condition through a QoS rule comment. The supplied rating indicates potentially complete compromise or disruption. Public exploit information exists, but the sources do not establish active exploitation or identify a fixed firmware release.
Executive priority
Treat confirmed affected devices as an urgent remediation priority because public exploit information and potentially complete impact materially raise risk. Prioritize externally reachable or broadly accessible devices first. Do not describe the issue as actively exploited without new evidence.
Technical view
CVE-2026-19811 is a stack-based buffer overflow in firewall.so's setIpQosRules function, reached through /cgi-bin/cstecgi.cgi. Manipulating the Comment argument affects A800R firmware 4.1.2cu.5137_B20200730. The supplied CVSS v2 vector is 9.0 and indicates network reachability, low complexity, single authentication, and potentially complete confidentiality, integrity, and availability impact.
Likely exposure
Exposure is limited to TOTOLINK A800R devices running the specifically listed firmware. Risk is greatest where the vulnerable CGI interface is reachable from untrusted networks or accessible through weak or compromised credentials. The bundle does not identify other models or versions as affected.
Exploitation context
Technical exploit information has been published publicly, increasing the possibility of attempted abuse. However, this CVE is not listed as KEV in the supplied bundle, and no cited source establishes exploitation in the wild. Authentication appears required according to the supplied CVSS v2 vector.
Researcher notes
The supplied evidence identifies the vulnerable function, endpoint, argument, weakness class, and exact firmware. It does not establish successful code execution, exploitation in the wild, a vendor patch, or additional affected versions. Validation should remain non-destructive; avoid reproducing the overflow on production equipment.
Mitigation direction
- Inventory TOTOLINK A800R devices and identify firmware version 4.1.2cu.5137_B20200730.
- Restrict the device administration interface to trusted networks and authorized administrators.
- Disable external access to the administration interface where operationally feasible.
- Check TOTOLINK guidance for corrected firmware; no fixed release is identified in the supplied sources.
- Replace or isolate affected devices if supported corrected firmware is unavailable.
Validation and detection
- Confirm each A800R firmware version through trusted administrative or asset-management records.
- Verify the vulnerable CGI interface is not exposed to untrusted networks.
- Review authentication and network logs for unusual QoS configuration activity or repeated failures.
- Confirm access controls permit only authorized administrators from trusted management networks.
- Document vendor guidance and verify any remediation against the exact model and firmware.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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-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 lookupCWE-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 lookupCVE-2026-19811 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- 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
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.
SSVC decision data
CVSS vector scores
4 official scoresWe 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.
AV:N/AC:L/Au:S/C:C/I:C/A:C/E:POC/RL:ND/RC:UR810VulDBCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:X/RC:R2.85.9VulDBCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:X/RC:R2.85.9VulDBCVSS: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——VulDBVulnerability scoring details
Base CVSS 4.0 score
8.7HighVector: 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
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:X/RC:R
Base CVSS 3.0 score
8.8HighVector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:X/RC:R
Base CVSS 2.0 score
9CriticalVector: AV:N/AC:L/Au:S/C:C/I:C/A:C/E:POC/RL:ND/RC:UR
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- Source timelineVulDB
Advisory disclosed
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- Source timelineVulDB
VulDB entry created
- Source timelineVulDB
VulDB entry last update
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- VDB-389947 | TOTOLINK A800R firewall.so cstecgi.cgi setIpQosRules stack-based overflowCVE reference, VulDB · vdb-entry, technical-description
- VDB-389947 | CTI Indicators (IOB, IOC, IOA)CVE reference, VulDB · signature, permissions-required
- CVE-2026-19811 | CVE Analysis and ReportCVE reference, VulDB · third-party-advisory
- Submit #869425 | Totolink A800R V4.1.2cu.5137_B20200730 Buffer OverflowCVE reference, VulDB · third-party-advisory
- https://github.com/panda666-888/vuls/blob/main/totolink/a800r/setIpQosRules.mdCVE reference, VulDB · exploit
- https://www.totolink.net/CVE reference, VulDB · product
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Restriction of Operations within the Bounds of a Memory Buffer
Improper Restriction of Operations within the Bounds of a Memory Buffer represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Stack-based Buffer Overflow
Stack-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.