CVE-2026-45537

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.

CVSS v3 9.1 CRITICAL

9.1^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

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

Configurations

No configuration.

History

No history.

Information

Published : 2026-08-04 23:16

Updated : 2026-09-08 20:41

NVD link : CVE-2026-45537

Mitre link : CVE-2026-45537

CVE.ORG link : CVE-2026-45537

JSON object : View

Products Affected

No product.

CWE

CWE-120

Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

{"id": "CVE-2026-45537", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-45537", "role": "CISA Coordinator", "options": [{"exploitation": "poc"}, {"automatable": "yes"}, {"technicalImpact": "total"}], "version": "2.0.3", "timestamp": "2026-08-05T17:47:59.631408Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "security-advisories@github.com", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 9.1, "attackVector": "NETWORK", "baseSeverity": "CRITICAL", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}, "impactScore": 5.2, "exploitabilityScore": 3.9}]}, "affected": [{"source": "security-advisories@github.com", "affectedData": [{"vendor": "OpenSIPS", "product": "opensips", "versions": [{"status": "affected", "version": ">= 3.4.0, < 3.6.6"}, {"status": "affected", "version": ">= 4.0.0-beta, < 4.0.0-rc1"}]}]}], "published": "2026-08-04T23:16:51.687", "references": [{"url": "https://github.com/OpenSIPS/opensips/commit/4d23613b65579b073784a07a65d3bf52443a4efb", "source": "security-advisories@github.com"}, {"url": "https://github.com/OpenSIPS/opensips/commit/5f103effaf5f372cccffe0b138f16998eba12668", "source": "security-advisories@github.com"}, {"url": "https://github.com/OpenSIPS/opensips/security/advisories/GHSA-v7h4-fwrc-c66v", "source": "security-advisories@github.com"}, {"url": "https://github.com/OpenSIPS/opensips/security/advisories/GHSA-v7h4-fwrc-c66v", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}], "vulnStatus": "Awaiting Analysis", "weaknesses": [{"type": "Secondary", "source": "security-advisories@github.com", "description": [{"lang": "en", "value": "CWE-120"}]}], "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."}], "lastModified": "2026-09-08T20:41:31.497", "sourceIdentifier": "security-advisories@github.com"}