CVE-2026-45538
OpenSIPS: Stack Buffer Overflow in sip_to_json() Header Name Copy
Description
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.
INFO
Published Date :
Aug. 4, 2026, 9:16 p.m.
Last Modified :
Aug. 4, 2026, 9:16 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-45538
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | CRITICAL | [email protected] |
Solution
- Update OpenSIPS to a patched version.
- Avoid calling sip_to_json with long header names.
- Apply vendor-provided security patches.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-45538.
| URL | Resource |
|---|---|
| https://github.com/OpenSIPS/opensips/security/advisories/GHSA-37wc-5j8j-95x3 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-45538 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-45538
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-45538 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-45538 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Aug. 04, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'OpenSIPS', 'product': 'opensips', 'versions': [{'status': 'affected', 'version': '<= 4.0.0'}]}] Added Description 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Added CWE CWE-121 Added Reference https://github.com/OpenSIPS/opensips/security/advisories/GHSA-37wc-5j8j-95x3