CVE-2026-45537

Description

OpenSIPS is a Session Initiation Protocol (SIP) server implementation. In versions prior to 3.6.6 and 4.0.0-rc1, the construct_uri() function concatenates multiple URI components (protocol, username, domain, port, params) into a fixed 1024-byte global BSS buffer without any bounds checking. When a routing script calls construct_uri() with an attacker-controlled username, a combined component length exceeding 1024 bytes overflows the buffer, corrupting adjacent global data with attacker-controlled content. The overflow reaches disable_503_translation, a global flag controlling SIP 503 response handling, allowing an attacker to deterministically set the flag via the URI username and alter the server's routing behavior for subsequent messages. Because the same buffer is shared with contact_builder(), the overflow also corrupts that function's data, and without a memory sanitizer the adjacent globals are silently overwritten on every request containing a long username. This issue has been fixed in versions 3.6.6 and 4.0.0-rc1.

Overview

State: PUBLISHED
Assigner (CNA): GitHub_M
CVSS severity: CRITICAL
CVSS score: 9.1 / 10
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Effective score: 9.1 / 10 CRITICAL source: CNA overview
CWE(s): CWE-120
Reserved: 2026-05-12
Published: 2026-08-04 22:48 UTC
Last updated: 2026-08-04 22:48 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/45xxx/CVE-2026-45537.json
Linked Threat: CVE-2026-45537 — OpenSIPS: Global Buffer Overflow in construct_uri

Affected products (1)

Vendor	Product	Versions	Platforms
OpenSIPS	opensips	`>= 3.4.0, < 3.6.6` (affected), `>= 4.0.0-beta, < 4.0.0-rc1` (affected)	—

Vendor references (3)

References embedded in the original CVE record by the assigning CNA.

https://github.com/OpenSIPS/opensips/security/advisories/GHSA-v7h4-fwrc-c66v x_refsource_CONFIRM
https://github.com/OpenSIPS/opensips/commit/4d23613b65579b073784a07a65d3bf52443a4efb x_refsource_MISC
https://github.com/OpenSIPS/opensips/commit/5f103effaf5f372cccffe0b138f16998eba12668 x_refsource_MISC

Web references (0)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

No web references attached yet.

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-45537.json.

{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "opensips",
          "vendor": "OpenSIPS",
          "versions": [
            {
              "status": "affected",
              "version": ">= 3.4.0, < 3.6.6"
            },
            {
              "status": "affected",
              "version": ">= 4.0.0-beta, < 4.0.0-rc1"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "OpenSIPS is a Session Initiation Protocol (SIP) server implementation. In versions prior to 3.6.6 and 4.0.0-rc1, the construct_uri() function concatenates multiple URI components (protocol, username, domain, port, params) into a fixed 1024-byte global BSS buffer without any bounds checking. When a routing script calls construct_uri() with an attacker-controlled username, a combined component length exceeding 1024 bytes overflows the buffer, corrupting adjacent global data with attacker-controlled content. The overflow reaches disable_503_translation, a global flag controlling SIP 503 response handling, allowing an attacker to deterministically set the flag via the URI username and alter the server's routing behavior for subsequent messages. Because the same buffer is shared with contact_builder(), the overflow also corrupts that function's data, and without a memory sanitizer the adjacent globals are silently overwritten on every request containing a long username. This issue has been fixed in versions 3.6.6 and 4.0.0-rc1."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 9.1,
            "baseSeverity": "CRITICAL",
            "confidentialityImpact": "NONE",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-120",
              "description": "CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-04T22:48:43.580Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/OpenSIPS/opensips/security/advisories/GHSA-v7h4-fwrc-c66v",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/OpenSIPS/opensips/security/advisories/GHSA-v7h4-fwrc-c66v"
        },
        {
          "name": "https://github.com/OpenSIPS/opensips/commit/4d23613b65579b073784a07a65d3bf52443a4efb",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/OpenSIPS/opensips/commit/4d23613b65579b073784a07a65d3bf52443a4efb"
        },
        {
          "name": "https://github.com/OpenSIPS/opensips/commit/5f103effaf5f372cccffe0b138f16998eba12668",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/OpenSIPS/opensips/commit/5f103effaf5f372cccffe0b138f16998eba12668"
        }
      ],
      "source": {
        "advisory": "GHSA-v7h4-fwrc-c66v",
        "discovery": "UNKNOWN"
      },
      "title": "OpenSIPS: Global Buffer Overflow in construct_uri"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-45537",
    "datePublished": "2026-08-04T22:48:43.580Z",
    "dateReserved": "2026-05-12T17:48:47.878Z",
    "dateUpdated": "2026-08-04T22:48:43.580Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}