How severe is CVE-2021-42659?

CVE-2021-42659 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-42659 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-42659?

CVE-2021-42659 primarily affects Tenda Ac9 Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-42659?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-42659 published?

CVE-2021-42659 was published on 2022-05-24 and last updated on 2026-06-17.

CVE-2021-42659

CVE-2021-42659 is a medium-severity vulnerability in Tenda Ac9 Firmware with a CVSS 3.x base score of 6.5. 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-119.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 6.1
EPSS exploit prediction: 1% (54th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-119
Affected product: Tenda Ac9 Firmware
Published: 2022-05-24
Last modified: 2026-06-17

Description

There is a buffer overflow vulnerability in the Web server httpd of the router in Tenda router devices such as Tenda AC9 V1.0 V15.03.02.19(6318) and Tenda AC9 V3.0 V15.03.06.42_multi. When setting the virtual service, the httpd program will crash and exit when the super-long list parameter occurs.

Frequently asked questions

What is CVE-2021-42659?: There is a buffer overflow vulnerability in the Web server httpd of the router in Tenda router devices such as Tenda AC9 V1.0 V15.03.02.19(6318) and Tenda AC9 V3.0 V15.03.06.42_multi. When setting the virtual service, the httpd program will crash and exit when the super-long list parameter occurs.
How severe is CVE-2021-42659?: CVE-2021-42659 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-42659 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-42659?: CVE-2021-42659 primarily affects Tenda Ac9 Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-42659?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-42659 published?: CVE-2021-42659 was published on 2022-05-24 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:o:tenda:ac9_firmware:15.03.05.19\(6318\):*:*:*:*:*:*:*
cpe:2.3:o:tenda:ac9_firmware:15.03.06.42_multi:*:*:*:*:*:*:*

More vulnerabilities in Tenda Ac9 Firmware

CVE-2025-45042 — Critical (CVSS 9.8): Tenda AC9 v15.03.05.14 was discovered to contain a command injection vulnerability via the Telnet function.
CVE-2025-44877 — Critical (CVSS 9.8): Tenda AC9 V15.03.06.42_multi was found to contain a command injection vulnerability in the formSetSambaConf function…
CVE-2025-44872 — Critical (CVSS 9.8): Tenda AC9 V15.03.06.42_multi was found to contain a command injection vulnerability in the formsetUsbUnload function…
CVE-2025-45429 — Critical (CVSS 9.8): In the Tenda ac9 v1.0 router with firmware V15.03.05.14_multi, there is a stack overflow vulnerability in…
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CVE-2025-45427 — Critical (CVSS 9.8): In Tenda AC9 v1.0 with firmware V15.03.05.14_multi, the security parameter of /goform/WifiBasicSet has a stack overflow…

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