CVE-2021-27245

Q: How do I fix CVE-2021-27245?

Upgrade archer a7 firmware to a7(us)_v5_200220 or later.

Q: Is CVE-2021-27245 being actively exploited?

Not that we know of. CVE-2021-27245 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 3.2% is the estimated probability that it will be exploited in the next 30 days. That is higher than 87% of all scored CVEs.

Q: How severe is CVE-2021-27245?

CVE-2021-27245 has a CVSS v3 base score of 8.1, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

Q: What does CVE-2021-27245 affect?

Published advisories record a fix for archer a7 firmware (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

HIGHEPSS 87th pctl

8.1

CVSS v3

NVD

Description

This vulnerability allows a firewall bypass on affected installations of TP-Link Archer A7 prior to Archer C7(US)_V5_210125 and Archer A7(US)_V5_200220 AC1750 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the handling of IPv6 connections. The issue results from the lack of proper filtering of IPv6 SSH connections. An attacker can leverage this in conjunction with other vulnerabilities to execute code in the context of root. Was ZDI-CAN-12309.

CWE-693Protection Mechanism Failure

How to fix

Remediation Available

archer a7 firmwareNVD

Affected:< a7(us)_v5_200220Fixed in:a7(us)_v5_200220CVE-2021-27245derived from NVD

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

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 ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

3.21%probability of exploitation in 30 days

87thpercentile

Elevated risk: more likely to be exploited than 87% of all known CVEs.

References

Third-Party Advisory1

zerodayinitiative.com

Related Vulnerabilities

Other CWE-693 (Protection Mechanism Failure) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2013-2465	Critical	9.8	99%	KEV + Ransom	-
CVE-2024-21412	High	8.1	95%	KEV + Ransom	Fix
CVE-2013-0431	Medium	5.3	90%	KEV + Ransom	-
CVE-2019-1003030	Critical	9.9	76%	KEV	-
CVE-2025-40536	High	8.1	72%	KEV	Fix
CVE-2025-0411	High	7.0	67%	KEV	Fix

Common questions

How do I fix CVE-2021-27245?

Upgrade archer a7 firmware to a7(us)_v5_200220 or later.

Is CVE-2021-27245 being actively exploited?

Not that we know of. CVE-2021-27245 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 3.2% is the estimated probability that it will be exploited in the next 30 days. That is higher than 87% of all scored CVEs.

How severe is CVE-2021-27245?

CVE-2021-27245 has a CVSS v3 base score of 8.1, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2021-27245 affect?

Published advisories record a fix for archer a7 firmware (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

Embed a live status badge for CVE-2021-27245

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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 2024-11-21.