CVE-2021-27137

Exploitation

Exploited in the wild. Listed in the CISA Known Exploited Vulnerabilities catalog on 2026-07-21. Federal remediation due 2026-07-24.

SSVC decision

• ExploitationactiveCISA reports credible evidence of active exploitation.
• AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
• Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

4.00% probability of exploitation activity in the next 30 days.

EPSS percentile

Ranks above 89.7% of scored records. A rank, not a probability.

NVD base score

8.1 (CVSS v3.x), scored by the NVD independently of the CNA.

NVD CVSS vector

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

NVD analysis status

Analyzed. NVD last modified this record on 2026-07-22.

Red Hat severity

No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2026-07-16 00:00Z1 MO AGO

Last updated

2026-07-22 03:55Z1 MO AGO

Reserved

2021-02-10

Assigning CNA

mitre

Record state

PUBLISHED

Severity

High (CVSS 8.1)

CNA CVSS vector

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

Weaknesses

• CWE-121Stack-based Buffer OverflowVariant

Data version

5.2

Document digest

b59d0a73c787f5f0780c3d39b0f636617afc23b091f8761cbbe2ab833b48c623

• svn.dd-wrt.comhttps://svn.dd-wrt.com/changeset/45724
• ssd-disclosure.comhttps://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/
• securityaffairs.comhttps://securityaffairs.com/193290/uncategorized/iot-botnet-c0xmo-adds-competitor-killing-capability.html
• www.bleepingcomputer.comhttps://www.bleepingcomputer.com/news/security/c0xmo-botnet-spreads-via-dd-wrt-router-flaw-kills-rival-malware/
• www.fortinet.comhttps://www.fortinet.com/blog/threat-research/inside-cross-platform-propagation-of-new-gafgyt-variant-c0xmo
• www.cisa.govhttps://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27137government-resource