How severe is CVE-2021-47854?

CVE-2021-47854 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-2021-47854 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2021-47854?

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.

Does CVE-2021-47854 have an EU (EUVD) identifier?

Yes. CVE-2021-47854 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-3629.

When was CVE-2021-47854 published?

CVE-2021-47854 was published on 2026-01-21 and last updated on 2026-06-17.

CVE-2021-47854

CVE-2021-47854 is a critical-severity vulnerability 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 v4: 8.7
EPSS exploit prediction: 1% (58th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-3629
Weakness: CWE-120
Published: 2026-01-21
Last modified: 2026-06-17

Description

DD-WRT version 45723 contains a buffer overflow vulnerability in the UPNP network discovery service that allows remote attackers to potentially execute arbitrary code. Attackers can send crafted M-SEARCH packets with oversized UUID payloads to trigger buffer overflow conditions on the target device.

Frequently asked questions

What is CVE-2021-47854?: DD-WRT version 45723 contains a buffer overflow vulnerability in the UPNP network discovery service that allows remote attackers to potentially execute arbitrary code. Attackers can send crafted M-SEARCH packets with oversized UUID payloads to trigger buffer overflow conditions on the target device.
How severe is CVE-2021-47854?: CVE-2021-47854 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-2021-47854 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2021-47854?: 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.
Does CVE-2021-47854 have an EU (EUVD) identifier?: Yes. CVE-2021-47854 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-3629.
When was CVE-2021-47854 published?: CVE-2021-47854 was published on 2026-01-21 and last updated on 2026-06-17.

References

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