Is CVE-2021-45756 in the CISA KEV catalog?

No. CVE-2021-45756 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-45756?

CVE-2021-45756 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2021-45756?

CVE-2021-45756 has an EPSS score of 1.74% (75th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-45756?

Upgrade rt-ac5300 firmware to 3.0.0.4.384.82072 or later. Fixes are available for 2 affected products.

CVE & CISA-KEV Catalog

CVE-2021-45756

CRITICALEPSS 75th pctl

9.8

CVSS v3

NVD

Description

Asus RT-AC68U <3.0.0.4.385.20633 and RT-AC5300 <3.0.0.4.384.82072 are affected by a buffer overflow in blocking_request.cgi.

CWE-120Classic Buffer Overflow

How to fix

Remediation Available

rt-ac5300 firmwareNVD

Affected:< 3.0.0.4.384.82072Fixed in:3.0.0.4.384.82072CVE-2021-45756derived from NVD

rt-ac68u firmwareNVD

Affected:< 3.0.0.4.385.20633Fixed in:3.0.0.4.385.20633CVE-2021-45756derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploit Intelligence

1.74%probability of exploitation in 30 days

75thpercentile

Elevated risk: more likely to be exploited than 75% of all known CVEs.

References

Exploit1

github.com

Vendor Advisory1

asus.com

Other references1

rt-ac68u.com

Related Vulnerabilities

Other CWE-120 (Classic Buffer Overflow) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2014-0195	Medium	6.8	100%	-	Fix
CVE-2017-7269	Critical	9.8	100%	KEV	-
CVE-2019-11043	High	8.7	99%	KEV + Ransom	Fix
CVE-2011-4862	High	10.0	95%	-	Fix
CVE-2007-5659	High	7.8	94%	KEV	Fix
CVE-2022-3786	High	7.5	91%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-05.