CVE-2026-100070
Received Received - Intake

SIP Header Parsing Flaw in Linux Kernel NAT

Publication date: 2026-09-25

Last updated on: 2026-09-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_nat_sip: rewind offset when NAT shrinks the packet sashiko says: If map_addr() changes the packet length, such as when the public NAT IP string is shorter or longer than the internal IP, coff will still point to the offset relative to the pre-mangled packet. If the packet shrinks, coff could overshoot the correct position, potentially causing the next ct_sip_parse_header_uri() call to silently skip bytes and miss subsequent Contact headers. Could this lead to a failure to NAT those subsequent headers and leak internal network details?

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Meta Information

Published
2026-09-25
Last Modified
2026-09-25
Generated
2026-09-25
AI Q&A
2026-09-25
EPSS Evaluated
N/A
NVD
CVE-2026-100070
EUVD
EUVD-2026-87067

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability affects the Linux kernel's netfilter SIP NAT handling. When the NAT IP address string is shorter or longer than the internal IP, the packet length changes but the offset calculation for parsing SIP headers remains based on the original packet size. This can cause the parser to skip bytes and miss subsequent SIP headers like Contact headers, potentially leaking internal network details.

Impact Analysis

If exploited, this flaw could allow an attacker to manipulate SIP traffic in a way that bypasses NAT protections. This might expose internal network information such as IP addresses or routing details through improperly parsed SIP headers. Systems relying on SIP for VoIP or messaging could experience disrupted services or unauthorized data exposure.

Mitigation Strategies

Apply the latest Linux kernel patches to address the nf_nat_sip vulnerability. Monitor network traffic for SIP header manipulation attempts and ensure NAT configurations do not alter packet lengths unexpectedly.

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