CVE-2026-73261 (GCVE-0-2026-73261)

Vulnerability from cvelistv5 – Published: 2026-10-14 18:25 – Updated: 2026-10-14 18:25
VLAI
Title
Mongoose: handle_opt() missing opts[1] > len check — 1-byte OOB read corrupts TCP MSS, silences mg_send() per connection
Summary
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.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE
  • CWE-20 - Improper Input Validation
  • CWE-125 - Out-of-bounds Read
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7712 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
cesanta mongoose Affected: < 7.23
guessed Create a notification for this product.
Show details on NVD website
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{
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          "value": "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."
        }
      ],
      "metrics": [
        {
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            "attackVector": "NETWORK",
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            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
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            "version": "3.1"
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              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-125",
              "description": "CWE-125: Out-of-bounds Read",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-14T18:25:41.102Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/cesanta/mongoose/security/advisories/GHSA-3fmr-92g4-wchx",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/cesanta/mongoose/security/advisories/GHSA-3fmr-92g4-wchx"
        },
        {
          "name": "https://github.com/cesanta/mongoose/commit/cc7c6d2d18c28fcc6d085633dddd88402946140a",
          "tags": [
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          ],
          "url": "https://github.com/cesanta/mongoose/commit/cc7c6d2d18c28fcc6d085633dddd88402946140a"
        },
        {
          "name": "https://github.com/cesanta/mongoose/releases/tag/7.23",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/cesanta/mongoose/releases/tag/7.23"
        }
      ],
      "source": {
        "advisory": "GHSA-3fmr-92g4-wchx",
        "discovery": "UNKNOWN"
      },
      "title": "Mongoose: handle_opt() missing opts[1] \u003e len check \u2014 1-byte OOB read corrupts TCP MSS, silences mg_send() per connection"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-73261",
    "datePublished": "2026-10-14T18:25:41.102Z",
    "dateReserved": "2026-08-11T17:18:01.598Z",
    "dateUpdated": "2026-10-14T18:25:41.102Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
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      "date": "2026-10-15",
      "epss": "0.00349",
      "percentile": "0.26933"
    },
    "nvd": {
      "cve": {
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                "product": "mongoose",
                "vendor": "cesanta",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003c 7.23"
                  }
                ]
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            "source": "security-advisories@github.com"
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "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."
          }
        ],
        "id": "CVE-2026-73261",
        "lastModified": "2026-10-14T19:17:19.990",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 7.5,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "NONE",
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                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
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        "references": [
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            "url": "https://github.com/cesanta/mongoose/commit/cc7c6d2d18c28fcc6d085633dddd88402946140a"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/cesanta/mongoose/releases/tag/7.23"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/cesanta/mongoose/security/advisories/GHSA-3fmr-92g4-wchx"
          }
        ],
        "sourceIdentifier": "security-advisories@github.com",
        "vulnStatus": "Received",
        "weaknesses": [
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            "description": [
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                "lang": "en",
                "value": "CWE-20"
              },
              {
                "lang": "en",
                "value": "CWE-125"
              }
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            "source": "security-advisories@github.com",
            "type": "Primary"
          }
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    },
    "redhat_vex": {
      "current_release_date": "2026-10-15T18:39:11+00:00",
      "cve": "CVE-2026-73261",
      "id": "CVE-2026-73261",
      "initial_release_date": "2026-10-14T18:25:41.102000+00:00",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "mongoose: mongoose: Denial of Service via malformed TCP options",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-73261.json",
      "version": "3"
    }
  }
}



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