CVE-2026-45538Public exploitNetwork attack vector

Pre-auth code execution via unchecked header copy

Published Aug 4, 2026 · Updated Aug 4, 2026

Stack-based buffer overflow in OpenSIPS 4.0.0 and earlier allows remote attackers to crash the server or execute code via SIP. sip_to_json() copies an unbounded SIP header name into a 255-byte stack buffer, allowing attacker-controlled data to overwrite saved registers and the return address. Exposure requires a routing script that invokes sip_to_json(); one unauthenticated UDP or TCP message can crash the process, while code execution depends on build hardening.

CVSS severity9.8
Critical
EPSS probability0.58%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in OpenSIPS 4.0.0 and earlier allows remote attackers to crash the server or execute code via SIP. sip_to_json() copies an unbounded SIP header name into a 255-byte stack buffer, allowing attacker-controlled data to overwrite saved registers and the return address. Exposure requires a routing script that invokes sip_to_json(); one unauthenticated UDP or TCP message can crash the process, while code execution depends on build hardening.

The record

CVE
CVE-2026-45538
Published
Aug 4, 2026
Updated
Aug 4, 2026
Vendor
OpenSIPS
Product
OpenSIPS
Classifications
CWE-121, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 4, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=<= 4.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenSIPS · OpenSIPSversion=<= 4.0.0

Published CVSS scores

9.8GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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