CVE-2021-31755
Memory Safety in Tenda Ac11 Firmware ≤ 02.03.01.104_cn
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2021-31755 is a critical-severity Out-of-bounds Write (CWE-787) vulnerability in Tenda Ac11 Firmware. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Security Account Manager (T1003.002); ranked in the top 0.3% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
A stack buffer overflow vulnerability exists in Tenda AC11 wireless routers running firmware versions through 02.03.01.104_CN. The flaw is located in the /goform/setmac endpoint and is tracked as CWE-787. It carries a CVSS 3.1 base score of 9.8, reflecting network-accessible, unauthenticated attack complexity.
An unauthenticated attacker can send a crafted HTTP POST request to the affected endpoint and trigger the overflow to execute arbitrary code on the device. Successful exploitation grants full control of the router, enabling actions such as traffic interception, persistence, or lateral movement within the attached network.
The vulnerability appears in CISA's Known Exploited Vulnerabilities catalog, confirming observed in-the-wild exploitation. Public proof-of-concept material is available in repositories that demonstrate request construction against the setmac handler, underscoring the need for immediate firmware updates or network segmentation where patches are unavailable.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-18639
Vulnerability Data
An issue was discovered on Tenda AC11 devices with firmware through 02.03.01.104_CN. A stack buffer overflow vulnerability in /goform/setmac allows attackers to execute arbitrary code on the system via a crafted post request.
- CWE(s)
- KEV Date Added
- 03 November 2021
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Out-of-bounds writes that corrupt control flow or inject shellcode are rendered non-executable by the same memory protections.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Vulnerability scanning and recording can discover out-of-bounds write flaws so they can be remediated.
Patching or replacing vulnerable software directly eliminates known instances of this coding weakness.
Secure-development practices (static analysis, bounds checking, code review) are the primary means of preventing out-of-bounds writes.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.