# CVE-2026-106803: Kamailio stack buffer overflow in ims_registrar_pcscf module

Source: https://junglewise.ai/threats/cve-2026-106803-a-stack-based-buffer-overflow-exists-in-kamailio-v6-1-3-and-v6-1  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-02. Updated: 2026-11-02  
License: CC BY 4.0 with a link back

CVE-2026-106803 · Severity: info · Published 2026-11-02

Kamailio is a SIP server used for VoIP telephony and real-time communications. A stack-based buffer overflow in the P-CSCF (proxy call session control function) module allows an unauthenticated remote attacker to crash the server by sending a specially crafted SIP NOTIFY message with an oversized port parameter, resulting in service outage.

Technologies: [Kamailio](https://junglewise.ai/threats/technologies/kamailio). Vendors: [Kamailio](https://junglewise.ai/threats/vendors/kamailio).

## Quick answers

**Is CVE-2026-106803 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-106803 being exploited in the wild.

**How severe is CVE-2026-106803?** Informational severity, published 2 November 2026.

**Which products and versions are affected?** Kamailio v6.1.3, v6.1.4.

**Is there a fix for CVE-2026-106803?** Yes: fixed in Fixed in commit 2126143 (enlarges buffer to 6 bytes and validates port length to maximum 5 digits). Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-106803 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-106803?** Check whether you run Kamailio at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in Fixed in commit 2126143 (enlarges buffer to 6 bytes and validates port length to maximum 5 digits)

## Technical details

The ims_registrar_pcscf module's process_contact() function copies an attacker-controlled port value from a SIP NAT alias parameter into a 5-byte (later 6-byte) stack buffer without proper length validation. An unauthenticated remote attacker can send a crafted application/reginfo+xml NOTIFY message with an oversized port value to overflow the buffer, corrupt the stack, and terminate the P-CSCF process.

## Affected products

- Kamailio Kamailio v6.1.3, v6.1.4

## Timeline

- 2026-11-02: disclosed: CVE-2026-106803 published

## References

- [https://gist.github.com/hackeryounow/7d7ccc9ec501a5d8c9143b2e1bcc11cb](https://gist.github.com/hackeryounow/7d7ccc9ec501a5d8c9143b2e1bcc11cb)
- [https://github.com/kamailio/kamailio/commit/21261436492f0014930e804e20586e3833bb91b9](https://github.com/kamailio/kamailio/commit/21261436492f0014930e804e20586e3833bb91b9)

## Related threats

- [Kamailio stack buffer overflow in ims_qos_npn module](https://junglewise.ai/threats/cve-2026-106804-a-stack-based-buffer-overflow-exists-in-kamailio-v6-1-3-and-v6-1)
- [Kamailio sipt module buffer overflow in ISUP parser](https://junglewise.ai/threats/cve-2026-108822-a-vulnerability-was-detected-in-kamailio-up-to-6-0-7-6-1-3-the)
- [Kamailio heap buffer overflow in CDP Diameter Receiver](https://junglewise.ai/threats/cve-2026-93962-a-weakness-has-been-identified-in-kamailio-up-to-5-8-8-6-0-7-6-1)
- [Kamailio ims_registrar_pcscf double free in security agreement parsing](https://junglewise.ai/threats/cve-2026-52023-kamailio-ims-registrar-pcscf-double-free-in-security-agreement)
- [Kamailio IMS P-CSCF denial of service in REGISTER handling](https://junglewise.ai/threats/cve-2026-52022-kamailio-ims-p-cscf-denial-of-service-in-register-handling)