CVE-2021-27137
Actively exploited. CVE-2021-27137 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-07-21) — exploitation has been observed in the wild, and US federal agencies are required to remediate it under BOD 22-01. Treat patching as urgent.
CISA has added four new vulnerabilities to its Known Exploited Vulnerabilities (KEV) Catalog , based on evidence of active exploitation. CVE-2021-27137 DD-WRT Stack-Based Buffer Overflow Vulnerability CVE-2026-0770 Langflow Inclusion of Functionality from Untrusted Control Sphere Vulnerability CVE-2026-63030 WordPress Core Interpretation Conflict Vulnerability CVE-2026-60137 WordPress Core SQL Injection Vulnerability These types of vulnerabilities are frequent attack vectors for malicious cyber actors and pose significant risks to the federal enterprise. Binding Operational Directive (BOD) 26-04: Prioritizing Security Updates Based on Risk establishes vulnerability management requirements for Federal Civilian Executive Branch (FCEB) agencies. BOD 26-04 reinforces the importance of the KEV Catalog and requires federal agencies to prioritize rapid remediation of high-risk vulnerabilities, specifically those identified by Common Vulnerabilities and Exposures (CVEs) listed in CISA’s KEV Catalog on publicly exposed assets that grant total control of the asset post-exploitation, while deferring action for lower-risk vulnerabilities. BOD 26-04 further establishes basic expectations for when agencies must check whether threat actors compromised the system before the patch was applied. While BOD 26-04 applies only to FCEB agencies, CISA encourages all organizations to adopt risk-based vulnerability management and prioritize remediation of KEV Catalog vulnerabilities . CISA will continue to add vulnerabilities to the catalog that meet the specified criteria . Aware of an exploited vulnerability not currently listed in the KEV Catalog? Submit it for potential addition through CISA’s KEV Nomination Form . Potential KEV additions must have a CVE ID, evidence of exploitation, and clear mitigation guidance.
CSIRTS triage
- What
- CISA has added four new vulnerabilities to its Known Exploited Vulnerabilities Catalog based on evidence of active exploitation.
- Who is affected
- Federal agencies are affected as they must prioritize remediation of these vulnerabilities.
- Urgency
- Remediation is urgent due to the high risk and active exploitation of these vulnerabilities.
- Action
- Federal agencies should prioritize rapid remediation of the listed vulnerabilities.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Exploitation confirmedAlready exploited in the wild (CISA KEV) — the prediction phase is over. Patch now. Riskier than 97% of all EPSS-scored CVEs.
Advisory coverage (3)
- highexploitedCISA Adds Four Known Exploited Vulnerabilities to Catalogcisa · 2026-07-21
- criticalexploitedCVE-2021-27137: DD-WRT Stack-Based Buffer Overflow Vulnerabilitycisa-kev · 2026-07-21
- highexploitedCVE-2021-27137: An issue was discovered in router/upnp/src/ssdp.c in DD-WRT before 45724. An unsafe strcpy in …nvd · 2026-07-16
External references
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