Vulnerability Details CVE-2026-73256
Mongoose is an embedded web server and network library. Prior to 7.22, a remote unauthenticated attacker can exploit an HTTP/1.0 reverse-proxy deployment by sending a request with Transfer-Encoding: chunked and conflicting framing. The http_cb() function in src/http.c tests hm.proto.len with an impossible greater-than-eight condition even though mg_http_parse() requires an eight-byte protocol string, so is_http_1_0 is never set. Mongoose consequently processes chunked encoding that an HTTP/1.0 proxy can ignore, enabling request smuggling and unauthorized access or state changes. This issue is fixed in version 7.22.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.007
EPSS Ranking 50.1%
CVSS Severity
CVSS v3 Score 9.1
References
Products affected by CVE-2026-73256
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cpe:2.3:a:cesanta:mongoose:-
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cpe:2.3:a:cesanta:mongoose:3.2
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cpe:2.3:a:cesanta:mongoose:3.3
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cpe:2.3:a:cesanta:mongoose:3.4
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cpe:2.3:a:cesanta:mongoose:3.5
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cpe:2.3:a:cesanta:mongoose:3.6
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cpe:2.3:a:cesanta:mongoose:3.7
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cpe:2.3:a:cesanta:mongoose:3.8
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cpe:2.3:a:cesanta:mongoose:4.0
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cpe:2.3:a:cesanta:mongoose:4.1
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cpe:2.3:a:cesanta:mongoose:5.0
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cpe:2.3:a:cesanta:mongoose:5.1
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cpe:2.3:a:cesanta:mongoose:5.2
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cpe:2.3:a:cesanta:mongoose:5.3
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cpe:2.3:a:cesanta:mongoose:5.4
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cpe:2.3:a:cesanta:mongoose:5.5
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cpe:2.3:a:cesanta:mongoose:5.6
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cpe:2.3:a:cesanta:mongoose:6.0
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cpe:2.3:a:cesanta:mongoose:6.1
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cpe:2.3:a:cesanta:mongoose:6.10
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cpe:2.3:a:cesanta:mongoose:6.11
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cpe:2.3:a:cesanta:mongoose:6.12
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cpe:2.3:a:cesanta:mongoose:6.13
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cpe:2.3:a:cesanta:mongoose:6.14
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cpe:2.3:a:cesanta:mongoose:6.15
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cpe:2.3:a:cesanta:mongoose:6.16
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cpe:2.3:a:cesanta:mongoose:6.17
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cpe:2.3:a:cesanta:mongoose:6.18
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cpe:2.3:a:cesanta:mongoose:6.2
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cpe:2.3:a:cesanta:mongoose:6.3
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cpe:2.3:a:cesanta:mongoose:6.4
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cpe:2.3:a:cesanta:mongoose:6.5
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cpe:2.3:a:cesanta:mongoose:6.6
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cpe:2.3:a:cesanta:mongoose:6.7
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cpe:2.3:a:cesanta:mongoose:6.8
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cpe:2.3:a:cesanta:mongoose:6.9
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cpe:2.3:a:cesanta:mongoose:7.0
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cpe:2.3:a:cesanta:mongoose:7.1
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cpe:2.3:a:cesanta:mongoose:7.10
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cpe:2.3:a:cesanta:mongoose:7.11
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cpe:2.3:a:cesanta:mongoose:7.12
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cpe:2.3:a:cesanta:mongoose:7.13
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cpe:2.3:a:cesanta:mongoose:7.14
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cpe:2.3:a:cesanta:mongoose:7.15
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cpe:2.3:a:cesanta:mongoose:7.16
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cpe:2.3:a:cesanta:mongoose:7.17
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cpe:2.3:a:cesanta:mongoose:7.18
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cpe:2.3:a:cesanta:mongoose:7.19
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cpe:2.3:a:cesanta:mongoose:7.2
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cpe:2.3:a:cesanta:mongoose:7.20
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cpe:2.3:a:cesanta:mongoose:7.21
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cpe:2.3:a:cesanta:mongoose:7.3
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cpe:2.3:a:cesanta:mongoose:7.4
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cpe:2.3:a:cesanta:mongoose:7.5
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cpe:2.3:a:cesanta:mongoose:7.6
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cpe:2.3:a:cesanta:mongoose:7.7
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cpe:2.3:a:cesanta:mongoose:7.8
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cpe:2.3:a:cesanta:mongoose:7.9