CVE-2026-45538
Critical · CVSS 9.8Published 2026-08-04
CVSS
9.8
Critical
EPSS
—
exploit probability
Active Exploit
No
not yet listed
What is CVE-2026-45538?
OpenSIPS is a Session Initiation Protocol (SIP) server implementation. In versions 4.0.0 and prior, processing a SIP message with a header name longer than 255 bytes causes a stack buffer overflow when sip_to_json() is called in the routing script. Function sip_to_json() (modules/sipmsgops/sipmsgops.c) copies SIP header names into a fixed 255-byte stack buffer without bounds checking, performing a memcpy of the full header-name length even though the SIP parser imposes no such limit (a header name can be roughly 65000 bytes). As a result, when a routing script calls sip_to_json(), a SIP message with a header name longer than 255 bytes triggers a stack buffer overflow in which both the length and content of the overwrite are attacker-controlled, corrupting the saved frame pointer and return address. A single unauthenticated UDP packet to the SIP port (5060) can crash the process or, on builds without stack protections, hijack the return address to achieve remote code execution. This affects deployments whose routing script invokes sip_to_json(). This issue was not fixed at the time of publication.
CVSS Score Explained
CVSS 9.8 is Critical — the highest severity tier. Attackers can likely exploit this remotely with no authentication and cause full system compromise. Patch immediately.
EPSS Exploitation Probability
No EPSS score yet — model needs more data on this CVE.
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