CVE-2026-45537

9.1 CRITICALpublic exploit available

Published 2026-08-04 · Updated 2026-08-05

AI risk analysis

Summary: The flaw in OpenSIPS allows an attacker to overflow a buffer by providing a long username, which can corrupt global data and alter the server's routing behavior.
Exploitability: Exploitation is relatively straightforward given the attacker can control the username length, but requires the target to be running an affected version.
Blast radius: If exploited, this could lead to deterministic control over the server's routing behavior, potentially allowing unauthorized access or denial of service.
Detection: No reliable host or network indicator is derivable from the published description.
Prioritized remediation: Upgrade to OpenSIPS 3.6.6 or 4.0.0-rc1 or later.

buffer-overflowrouting-alterationsips

Analysis generated locally by qwen2.5:7b-instruct (no data left the box). AI-assisted — verify against primary sources before acting.

NVD 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.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Weaknesses

CWE-120

Public exploit & PoC references

All references

Source data: NVD (nvd.nist.gov), public domain. Exploit-DB.ai adds local AI analysis for defensive use only.

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