High severity · published Apr 3, 2026
CVE-2026-23457
netfilter: nf_conntrack_sip: fix Content-Length u32 truncation in sip_help_tcp()
8.6
CVSS
0.4%
EPSS
No
On KEV
Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_sip: fix Content-Length u32 truncation in sip_help_tcp() sip_help_tcp() parses the SIP Content-Length header with simple_strtoul(), which returns unsigned long, but stores the result in unsigned int clen. On 64-bit systems, values exceeding UINT_MAX are silently truncated before computing the SIP message boundary. For example, Content-Length 4294967328 (2^32 + 32) is truncated to 32, causing the parser to miscalculate where the current message ends. The loop then treats trailing data in the TCP segment as a second SIP message and processes it through the SDP parser. Fix this by changing clen to unsigned long to match the return type of simple_strtoul(), and reject Content-Length values that exceed the remaining TCP payload length.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
Low
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 37% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
KE
Kernel · Linux
2.6.34 before 5.10.253; 5.11 before 5.15.203; 5.16 before 6.1.167; 6.2 before 6.6.130; 6.7 before 6.12.78; 6.13 before 6.18.20; +5 more · source: NVD
LI
Linux · Linux
f5b321bd37fbec9188feb1f721ab46a5ac0b35da before ed81b6a7012485acdb9c6c80735a0b7d8e5e1873; f5b321bd37fbec9188feb1f721ab46a5ac0b35da before cd1b7403ec835f8a0b3f1f7e68ac26af2cb1e42f; f5b321bd37fbec9188feb1f721ab46a5ac0b35da before b75209debb9adab287b3caa982f77788c1e15027; f5b321bd37fbec9188feb1f721ab46a5ac0b35da before 528b4509c9dfc272e2e92d811915e5211650d383; f5b321bd37fbec9188feb1f721ab46a5ac0b35da before 75fcaee5170e7dbbee778927134ef2e9568b4659; f5b321bd37fbec9188feb1f721ab46a5ac0b35da before 865dba58958c3a86786f89a501971ab0e3ec6ba9; +3 more · source: vendor
SS
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP · Siemens
V3.1.6; V3.1.5; V3.1.7; V3.1.6; V3.1.5; V3.1.7 · source: CISA
SS
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP · Siemens
V3.1.6; V3.1.5; V3.1.7; V3.1.6; V3.1.5; V3.1.7 · source: CISA
SS
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP · Siemens
V3.1.6; V3.1.5; V3.1.7 · source: CISA