Bug 2541421 (CVE-2026-100070)

Summary: CVE-2026-100070 kernel: netfilter: nf_nat_sip: rewind offset when NAT shrinks the packet
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in the Linux kernel. This vulnerability can result in information disclosure when processing Session Initiation Protocol (SIP) traffic through the netfilter Network Address Translation (NAT) helper. When address rewriting shortens a packet, the helper fails to adjust its internal offset, causing subsequent Contact headers to be skipped during translation. Consequently, an external recipient or network observer may receive untranslated internal IP addresses, exposing private network details.
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-25 13:26:53 UTC 
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?
Comment 1 Mauro Matteo Cascella 2026-09-30 16:57:17 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-100070.mbox