Security readout for executives and security teams
Plain-English summary
Tenda W20E devices running the identified firmware contain a memory-corruption flaw in QoS rule deletion. An authenticated remote user may trigger a stack overflow through a crafted QoS index, potentially disrupting or compromising the device. The public sources do not identify a vendor-confirmed fix.
Executive priority
Prioritize immediate exposure reduction and vendor follow-up. Public exploit availability, low reported complexity, and potential complete security impact justify urgent action, especially for externally reachable management interfaces. Replacement should be considered if Tenda provides no timely supported fix.
Technical view
CVE-2026-19823 affects formQOSRuleDel at /goform/delQos in Tenda W20E firmware 15.11.0.6(1068_1546_841)_CN_TDC. Improper handling of qosIndex causes a stack-based buffer overflow, classified as CWE-119 and CWE-121. The CVSS v2 vector describes network access, low complexity, and required authentication.
Likely exposure
Exposure is established only for Tenda W20E devices running the exact listed firmware. Risk is greatest where the management endpoint is reachable by untrusted or compromised authenticated users. The supplied evidence does not establish that other firmware versions or Tenda products are affected.
Exploitation context
A public exploit or proof of concept is referenced, increasing practical risk. Remote exploitation is reported, although the CVSS vector indicates authentication is required. The CVE is not listed as KEV in the supplied bundle, and no cited evidence confirms active exploitation in the wild.
Researcher notes
The vulnerable data path is qosIndex processing by formQOSRuleDel. The supplied evidence does not establish exploit reliability, demonstrated code execution, vendor acknowledgement, a patched version, or active exploitation. Avoid extrapolating affected versions from the wildcard firmware CPE without additional vendor evidence.
Mitigation direction
- Inventory Tenda W20E devices and identify those running the affected firmware.
- Restrict device administration to trusted management networks and authorized users.
- Check Tenda guidance and install a vendor-confirmed fixed firmware release when available.
- If no fix exists, isolate or replace affected devices according to business risk.
Validation and detection
- Confirm each device model and complete firmware build string.
- Determine whether the management interface is reachable from untrusted networks.
- Verify access controls prevent unauthorized users from reaching administrative endpoints.
- Review device logs, unexpected reboots, and crashes associated with QoS administration.
- Confirm remediation by recording the vendor-confirmed fixed firmware version after upgrading.
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-2026-19823 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
- Source timelineVulDB
VulDB entry created
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- 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-389956 | Tenda W20E QoS Rule Deletion delQos formQOSRuleDel stack-based overflowCVE reference, VulDB · vdb-entry, technical-description
- VDB-389956 | CTI Indicators (IOB, IOC, IOA)CVE reference, VulDB · signature, permissions-required
- CVE-2026-19823 | CVE Analysis and ReportCVE reference, VulDB · third-party-advisory
- Submit #869021 | Tenda W20E US_W20EV4.0br_V15.11.0.6(1068_1546_841)_CN_TDC.bin Buffer OverflowCVE reference, VulDB · third-party-advisory
- https://github.com/paueger/mycve/blob/main/Tenda_W20E/4.mdCVE reference, VulDB · exploit
- https://www.tenda.com.cn/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.