Unauthenticated code execution via UPnP UUID overflow
Published Jul 16, 2026 · Updated Jul 16, 2026
Stack-based buffer overflow in DD-WRT before 45724 allows remote attackers to execute code through a crafted UPnP M-SEARCH request. In ssdp_msearch, an unbounded strcpy copies the request's attacker-controlled ST:uuid value into a fixed 128-byte stack buffer. UPnP must be enabled, is disabled by default, and ordinarily listens only on internal interfaces; successful exploitation gains control of the router.
Summary
What happened
Stack-based buffer overflow in DD-WRT before 45724 allows remote attackers to execute code through a crafted UPnP M-SEARCH request. In ssdp_msearch, an unbounded strcpy copies the request's attacker-controlled ST:uuid value into a fixed 128-byte stack buffer. UPnP must be enabled, is disabled by default, and ordinarily listens only on internal interfaces; successful exploitation gains control of the router.
The record
- CVE
- CVE-2021-27137
- Published
- Jul 16, 2026
- Updated
- Jul 16, 2026
- Vendor
- DD-WRT
- Product
- DD-WRT
- Classifications
- CWE-121, T1210
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 16, 2026CVE publishedPublication date reported by the CVE source.
- Jul 16, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <45724
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- SSD DD-WRT UPnP buffer-overflow proof of conceptproof of concept · demonstrated
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Reported exploitation
Technologies
Your stack
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Your stack
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