CVE-2026-100070

Awaiting Analysis Awaiting Analysis - Queue

SIP Header Parsing Flaw in Linux Kernel NAT

Publication date: 2026-09-25

Last updated on: 2026-09-30

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?

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-09-25

Last Modified

2026-09-30

Generated

2026-10-16

AI Q&A

2026-09-25

EPSS Evaluated

2026-10-14

NVD

CVE-2026-100070

EUVD

EUVD-2026-87067

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

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.

Detection Guidance

This vulnerability requires kernel-level inspection of SIP traffic processed by the netfilter NAT module. Detection involves checking for SIP packet mishandling during NAT translation, particularly when public NAT IP length differs from internal IP. No direct commands are provided in the context to detect this issue.

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.

Compliance Impact

This vulnerability could potentially lead to the leakage of internal network details if subsequent SIP headers are not properly NATed due to incorrect offset handling. This may result in unauthorized exposure of sensitive information, which could impact compliance with data protection regulations like GDPR and HIPAA by failing to ensure confidentiality of personal or health data.

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.

Hi! I’m here to help you understand CVE-2026-100070. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70