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CVE-2026-45538— OpenSIPS: Stack Buffer Overflow in sip_to_json() Header Name Copy

Quick assessment

Affected
OpenSIPS opensips
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

OpenSIPS是OpenSIPS组织开源的一个 GPL 许可的 SIP 服务器实现。 OpenSIPS 4.0.0及之前版本存在缓冲区错误漏洞，该漏洞源于sip_to_json()函数在处理SIP消息时未进行边界检查，将超过255字节的头部名称复制到固定栈缓冲区，导致栈缓冲区溢出，可能允许未经身份验证的攻击者通过单个UDP数据包导致进程崩溃或远程代码执行。

CVSS 9.8 · Critical EPSS 0.80% · P56

Affected Version Matrix 1

VendorProduct Version RangeStatus
OpenSIPS opensips <= 4.0.0 affected
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I. Basic Information for CVE-2026-45538

Vulnerability Information
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Vulnerability Title
OpenSIPS: Stack Buffer Overflow in sip_to_json() Header Name Copy
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
栈缓冲区溢出
Source: CVE Program / CVE List V5
Vulnerability Title
OpenSIPS 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
OpenSIPS是OpenSIPS组织开源的一个 GPL 许可的 SIP 服务器实现。 OpenSIPS 4.0.0及之前版本存在缓冲区错误漏洞，该漏洞源于sip_to_json()函数在处理SIP消息时未进行边界检查，将超过255字节的头部名称复制到固定栈缓冲区，导致栈缓冲区溢出，可能允许未经身份验证的攻击者通过单个UDP数据包导致进程崩溃或远程代码执行。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
OpenSIPS opensips <= 4.0.0 -

II. Public POCs for CVE-2026-45538

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Qwen3.6-35B-A3B · 7582 chars
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III. Intelligence Information for CVE-2026-45538

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Vendor Advisories for CVE-2026-45538 (1)

Same Patch Batch · OpenSIPS · 2026-08-04 · 8 CVEs total

CVE-2026-45100 9.1 CRITICAL OpenSIPS: Buffer Overflow in Base64 Encode Transformation
CVE-2026-45537 9.1 CRITICAL OpenSIPS: Global Buffer Overflow in construct_uri
CVE-2026-45084 8.7 HIGH OpenSIPS: Denial of service in presence.handle_publish() from unchecked Content-Type state
CVE-2026-45809 8.7 HIGH OpenSIPS: Denial of Service in watcherinfo XML generation from oversized watcher URI
CVE-2026-46334 8.7 HIGH OpenSIPS: Denial of Service in SDP bandwidth parsing via QoS SDP cloning
CVE-2026-45103 7.5 HIGH OpenSIPS: SIP Message Smuggling via TCP Content-Length Integer Overflow
CVE-2026-45705 5.3 MEDIUM OpenSIPS: OOB Read in Multipart Body Boundary Parsing

IV. Related Vulnerabilities

Same product: opensips
Same vendor: OpenSIPS
Same weakness: CWE-121

V. Comments for CVE-2026-45538

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