How severe is CVE-2021-31756?

CVE-2021-31756 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-31756 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-31756?

CVE-2021-31756 affects Tenda Ac11 Firmware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-31756?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-31756 published?

CVE-2021-31756 was published on 2021-05-07 and last updated on 2026-06-17.

CVE-2021-31756

CVE-2021-31756 is a critical-severity vulnerability in Tenda Ac11 Firmware with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 10.0
EPSS exploit prediction: 3% (85th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Tenda Ac11 Firmware
Published: 2021-05-07
Last modified: 2026-06-17

Description

An issue was discovered on Tenda AC11 devices with firmware through 02.03.01.104_CN. A stack buffer overflow vulnerability in /gofrom/setwanType allows attackers to execute arbitrary code on the system via a crafted post request. This occurs when input vector controlled by malicious attack get copied to the stack variable.

Frequently asked questions

What is CVE-2021-31756?: An issue was discovered on Tenda AC11 devices with firmware through 02.03.01.104_CN. A stack buffer overflow vulnerability in /gofrom/setwanType allows attackers to execute arbitrary code on the system via a crafted post request. This occurs when input vector controlled by malicious attack get copied to the stack variable.
How severe is CVE-2021-31756?: CVE-2021-31756 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-31756 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-31756?: CVE-2021-31756 affects Tenda Ac11 Firmware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-31756?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-31756 published?: CVE-2021-31756 was published on 2021-05-07 and last updated on 2026-06-17.

References

https://github.com/Yu3H0/IoT_CVE/tree/main/Tenda/CVE_1

Affected products (1)

cpe:2.3:o:tenda:ac11_firmware:*:*:*:*:*:*:*:*

More vulnerabilities in Tenda Ac11 Firmware

CVE-2021-46321 — Critical (CVSS 9.8): Tenda AC Series Router AC11_V02.03.01.104_CN was discovered to contain a stack buffer overflow in the wifiBasicCfg…
CVE-2021-46265 — Critical (CVSS 9.8): Tenda AC Series Router AC11_V02.03.01.104_CN was discovered to contain a stack buffer overflow in the wanBasicCfg…
CVE-2021-46264 — Critical (CVSS 9.8): Tenda AC Series Router AC11_V02.03.01.104_CN was discovered to contain a stack buffer overflow in the onlineList…
CVE-2021-46263 — Critical (CVSS 9.8): Tenda AC Series Router AC11_V02.03.01.104_CN was discovered to contain a stack buffer overflow in the wifiTime module.…
CVE-2021-46262 — Critical (CVSS 9.8): Tenda AC Series Router AC11_V02.03.01.104_CN was discovered to contain a stack buffer overflow in the PPPoE module.…
CVE-2021-31758 — Critical (CVSS 9.8): An issue was discovered on Tenda AC11 devices with firmware through 02.03.01.104_CN. A stack buffer overflow…

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