CVE-2026-45100

Description

OpenSIPS is a Session Initiation Protocol (SIP) server implementation. Versions 3.4.0-beta through 3.6.5 and 4.0.0-beta contain a buffer overflow in the {s.b64encode} string transformation. The size check for {s.b64encode} only verifies that the input fits within the 64 KB transformation buffer, but base64 encoding expands the data by roughly a third, so an input between about 49,153 and 65,535 bytes produces more output than the buffer can hold and overflows it by up to 21,844 bytes. Because these transformation buffers sit next to each other in memory and are reused for chained transformations, the overflow writes attacker-controlled data into the adjacent buffer and corrupts values used by later transformations processing the same SIP message. A remote attacker can trigger this by sending a SIP message with a large header value (roughly 50,000 bytes or more) when the routing script applies {s.b64encode} to attacker-controlled input, making exploitability dependent on the deployment's routing configuration. 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: 2026-05-08
Published: 2026-08-04 21:41 UTC
Last updated: 2026-08-04 21:44 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/45xxx/CVE-2026-45100.json
Linked Threat: CVE-2026-45100 — OpenSIPS: Buffer Overflow in Base64 Encode Transformation

Affected products (1)

Vendor	Product	Versions	Platforms
OpenSIPS	opensips	`>= 3.4.0-beta, < 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-35fr-6rv9-vp68 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-2026-45100.json.

{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "opensips",
          "vendor": "OpenSIPS",
          "versions": [
            {
              "status": "affected",
              "version": ">= 3.4.0-beta, < 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. Versions 3.4.0-beta through 3.6.5 and 4.0.0-beta contain a buffer overflow in the {s.b64encode}\u00a0string transformation. The size check for {s.b64encode} only verifies that the input fits within the 64 KB transformation buffer, but base64 encoding expands the data by roughly a third, so an input between about 49,153 and 65,535 bytes produces more output than the buffer can hold and overflows it by up to 21,844 bytes. Because these transformation buffers sit next to each other in memory and are reused for chained transformations, the overflow writes attacker-controlled data into the adjacent buffer and corrupts values used by later transformations processing the same SIP message. A remote attacker can trigger this by sending a SIP message with a large header value (roughly 50,000 bytes or more) when the routing script applies \u00a0{s.b64encode}\u00a0 to attacker-controlled input, making exploitability dependent on the deployment's routing configuration. 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": "2026-08-04T21:44:40.109Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/OpenSIPS/opensips/security/advisories/GHSA-35fr-6rv9-vp68",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/OpenSIPS/opensips/security/advisories/GHSA-35fr-6rv9-vp68"
        },
        {
          "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-35fr-6rv9-vp68",
        "discovery": "UNKNOWN"
      },
      "title": "OpenSIPS: Buffer Overflow in Base64 Encode Transformation"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-45100",
    "datePublished": "2026-08-04T21:41:54.584Z",
    "dateReserved": "2026-05-08T19:27:26.698Z",
    "dateUpdated": "2026-08-04T21:44:40.109Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}