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TI-2021-08684 Aliases CVE-2021-27137GHSA-qx3v-2jx6-8m2c

Stack-based buffer overflow in DD-WRT

Priority CRITICAL 94Exploited in the wildCWE-121Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-121 and the CVSS impact.

Summary

An issue was discovered in router/upnp/src/ssdp.c in DD-WRT before 45724. An unsafe strcpy in the UPnP handling functionality allows an unauthenticated remote attacker to send a request that would overflow an internal fixed buffer. Exploitation requires the DD-WRT user to enable UPnP (which is off by default, and only listens on internal interfaces by default). This occurs in ssdp_msearch (reachable by an M-SEARCH request).

Why it matters now

Exploitation Active In CISA KEV since 2026-07-21CISA due date 2026-07-24
EPSS 0.03995 90th percentileScored 2026-11-07
Public exploit Yes 4 exploit referencesTagged by NVD
Fix Fixed DD-WRT (DD-WRT): 45724

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Active
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
DD-WRTDD-WRTbefore 4572445724Patch availableCNA
  • DD-WRT VendorDD-WRT Affected before 45724 Fixed in 45724 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:o:dd-wrt:dd-wrt:*:*:*:*:*:*:*:*before 45724VulnerableDD-WRT
  • cpe:2.3:o:dd-wrt:dd-wrt:*:*:*:*:*:*:*:* Versions before 45724 Vulnerable ·DD-WRT

Remediation

  • Fix · CNA DD-WRT (DD-WRT) Fixed in 45724

Timeline

  1. 2026-07-21 Added to CISA KEV
  2. 2026-10-02 Threatist record created from CVE-2021-27137
  3. 2026-10-03 Alias added: GHSA-qx3v-2jx6-8m2c

References

Exploit 4

Patch 1

  • TI-2022-10612 Out-of-bounds write in DD-WRT CVSS 3.1CRITICAL 9.8
  • TI-2009-02631 httpd.c in httpd in the management GUI in DD-WRT 24 sp1, and other versions before build… CVSS 2.0HIGH 8.3
  • TI-2020-10949 An issue was discovered in DD-WRT through 16214. CVSS 3.1HIGH 8.8
  • TI-2012-05124 Command Injection vulnerability exists via a CSRF in DD-WRT 24-sp2 from specially crafted… CVSS 3.1HIGH 8.8
  • TI-2009-02632 httpd.c in httpd in the management GUI in DD-WRT 24 sp1 does not require administrative… CVSS 2.0HIGH 7.5
  • TI-2008-06663 Multiple cross-site request forgery (CSRF) vulnerabilities in apply.cgi in DD-WRT 24 sp2… CVSS 2.0MEDIUM 6.8
See all 7 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences