| Title | Cesanta Mongoose Embedded Web Server 7.20 Insufficiently Random Values |
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| Description | The mg_sendnsreq() function in /src/dns.c generates DNS transaction IDs using a sequential counter that resets to 1 whenever the pending request list is empty. Since each resolved query is freed from the list before the next query is typically created, the transaction ID is a constant value of 1 for all non-overlapping DNS queries. This allows an attacker to spoof DNS responses with ~100% reliability without observing any prior traffic, completely bypassing the only authentication mechanism in the DNS protocol. The attack can be performed remotely by any host that can send UDP packets with a spoofed source IP to the victim, requires no authentication, and results in full control over hostname resolution -- enabling man-in-the-middle, credential theft, or redirection to malicious infrastructure. |
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| Source | ⚠️ https://github.com/dwBruijn/CVEs/blob/main/Mongoose/mg_sendnsreq.md |
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| User | dwbruijn (UID 93926) |
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| Submission | 02/10/2026 13:23 (2 months ago) |
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| Moderation | 02/22/2026 08:57 (12 days later) |
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| Status | Accepted |
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| VulDB entry | 347333 [Cesanta Mongoose up to 7.20 DNS Transaction ID /src/dns.c mg_sendnsreq random random values] |
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| Points | 20 |
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