How severe is CVE-2020-13391?

CVE-2020-13391 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-2020-13391 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-13391?

CVE-2020-13391 primarily affects Tendacn Ac6 Firmware. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-13391?

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-2020-13391 published?

CVE-2020-13391 was published on 2020-05-22 and last updated on 2026-06-17.

CVE-2020-13391

CVE-2020-13391 is a critical-severity vulnerability in Tendacn Ac6 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-120.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 3% (83rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-120
Affected product: Tendacn Ac6 Firmware
Published: 2020-05-22
Last modified: 2026-06-17

Description

An issue was discovered on Tenda AC6 V1.0 V15.03.05.19_multi_TD01, AC9 V1.0 V15.03.05.19(6318)_CN, AC9 V3.0 V15.03.06.42_multi, AC15 V1.0 V15.03.05.19_multi_TD01, and AC18 V15.03.05.19(6318_)_CN devices. There is a buffer overflow vulnerability in the router's web server -- httpd. While processing the /goform/SetSpeedWan speed_dir parameter for a POST request, a value is directly used in a sprintf to a local variable placed on the stack, which overwrites the return address of a function. An attacker can construct a payload to carry out arbitrary code execution attacks.

Frequently asked questions

What is CVE-2020-13391?: An issue was discovered on Tenda AC6 V1.0 V15.03.05.19_multi_TD01, AC9 V1.0 V15.03.05.19(6318)_CN, AC9 V3.0 V15.03.06.42_multi, AC15 V1.0 V15.03.05.19_multi_TD01, and AC18 V15.03.05.19(6318_)_CN devices. There is a buffer overflow vulnerability in the router's web server -- httpd. While processing the /goform/SetSpeedWan speed_dir parameter for a POST request, a value is directly used in a sprintf to a local variable placed on the stack, which overwrites the return address of a function. An attacker can construct a payload to carry out arbitrary code execution attacks.
How severe is CVE-2020-13391?: CVE-2020-13391 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-2020-13391 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-13391?: CVE-2020-13391 primarily affects Tendacn Ac6 Firmware. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-13391?: 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-2020-13391 published?: CVE-2020-13391 was published on 2020-05-22 and last updated on 2026-06-17.

References

Affected products (5)

cpe:2.3:o:tendacn:ac6_firmware:v15.03.05.19_multi_td01:*:*:*:*:*:*:*
cpe:2.3:o:tendacn:ac9_firmware:v15.03.05.19\(6318\):*:*:*:*:*:*:*
cpe:2.3:o:tendacn:ac15_firmware:v15.03.05.19_multi_td01:*:*:*:*:*:*:*
cpe:2.3:o:tendacn:ac18_firmware:v15.03.05.19\(6318\):*:*:*:*:*:*:*
cpe:2.3:o:tendacn:ac9_firmware:v15.03.06.42_multi:*:*:*:*:*:*:*

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CVE-2022-37176 — Critical (CVSS 9.8): Tenda AC6(AC1200) v5.0 Firmware v02.03.01.114 and below contains a vulnerability which allows attackers to remove the…
CVE-2020-13394 — Critical (CVSS 9.8): An issue was discovered on Tenda AC6 V1.0 V15.03.05.19_multi_TD01, AC9 V1.0 V15.03.05.19(6318)_CN, AC9 V3.0…
CVE-2020-13393 — Critical (CVSS 9.8): An issue was discovered on Tenda AC6 V1.0 V15.03.05.19_multi_TD01, AC9 V1.0 V15.03.05.19(6318)_CN, AC9 V3.0…
CVE-2020-13392 — Critical (CVSS 9.8): An issue was discovered on Tenda AC6 V1.0 V15.03.05.19_multi_TD01, AC9 V1.0 V15.03.05.19(6318)_CN, AC9 V3.0…
CVE-2020-13390 — Critical (CVSS 9.8): An issue was discovered on Tenda AC6 V1.0 V15.03.05.19_multi_TD01, AC9 V1.0 V15.03.05.19(6318)_CN, AC9 V3.0…
CVE-2020-13389 — Critical (CVSS 9.8): An issue was discovered on Tenda AC6 V1.0 V15.03.05.19_multi_TD01, AC9 V1.0 V15.03.05.19(6318)_CN, AC9 V3.0…

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