CVE-2026-73261

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Source
https://cve.org/CVERecord?id=CVE-2026-73261
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-73261.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-73261
Aliases
  • GHSA-3fmr-92g4-wchx
Downstream
Published
2026-10-14T18:25:41Z
Modified
2026-10-15T10:47:31Z
Severity
  • 7.5 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
Summary
Mongoose: handle_opt() missing opts[1] > len check — 1-byte OOB read corrupts TCP MSS, silences mg_send() per connection
Details

Mongoose is an embedded web server and network library. Prior to 7.23, the built-in TCP/IP stack enabled by MG_ENABLE_TCPIP in src/net_builtin.c does not reject a TCP option whose declared opts[1] length exceeds the remaining option bytes. In handle_opt(), a NOP followed by a truncated MSS option causes opts[3] to be read outside the declared options area and used as the low byte of dmss. An unauthenticated remote peer can corrupt the per-connection MSS value so later mg_send() calls transmit truncated or zero-length application payloads while the TCP connection otherwise appears healthy. This issue is fixed in version 7.23.

Database specific 
{
    "cna_assigner":  "GitHub_M",
    "cwe_ids":  [
        "CWE-125",
        "CWE-20"
    ],
    "osv_generated_from":  "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73261.json"
}
References

Affected packages

Git / github.com/cesanta/mongoose

Affected ranges

Type
GIT
Repo
https://github.com/cesanta/mongoose
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
02bdbb9ed6f0a8f7c42228c6e7cb35d748b60551
Database specific
Show details 
{
    "extracted_events":  [
        {
            "introduced":  "0"
        },
        {
            "fixed":  "7.23"
        }
    ],
    "source":  "AFFECTED_FIELD"
}

Affected versions

3.*
3.2
3.3
3.4
3.5
3.6
3.7
3.8
4.*
4.0
4.1
5.*
5.0
5.1
5.2
5.3
5.4
5.5
5.5_20140120
5.6
6.*
6.0
6.1
6.10
6.11
6.12
6.13
6.14
6.15
6.16
6.17
6.18
6.2
6.3
6.4
6.5
6.6
6.7
6.9
7.*
7.0
7.1
7.11
7.12
7.13
7.14
7.15
7.16
7.17
7.18
7.19
7.2
7.20
7.21
7.22
7.3
7.4
7.5
7.6
7.7
7.8

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-73261.json"