Linux kernel netfilter nf_conntrack_sip Content-Length truncation bug
CVE-2026-23457 Published on April 3, 2026
netfilter: nf_conntrack_sip: fix Content-Length u32 truncation in sip_help_tcp()
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.
Products Associated with CVE-2026-23457
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Affected Versions
Linux:- Version f5b321bd37fbec9188feb1f721ab46a5ac0b35da and below b75209debb9adab287b3caa982f77788c1e15027 is affected.
- Version f5b321bd37fbec9188feb1f721ab46a5ac0b35da and below 528b4509c9dfc272e2e92d811915e5211650d383 is affected.
- Version f5b321bd37fbec9188feb1f721ab46a5ac0b35da and below 75fcaee5170e7dbbee778927134ef2e9568b4659 is affected.
- Version f5b321bd37fbec9188feb1f721ab46a5ac0b35da and below 865dba58958c3a86786f89a501971ab0e3ec6ba9 is affected.
- Version f5b321bd37fbec9188feb1f721ab46a5ac0b35da and below d4f17256544cc37f6534a14a27a9dec3540c2015 is affected.
- Version f5b321bd37fbec9188feb1f721ab46a5ac0b35da and below fbce58e719a17aa215c724473fd5baaa4a8dc57c is affected.
- Version 2.6.34 is affected.
- Before 2.6.34 is unaffected.
- Version 6.1.167, <= 6.1.* is unaffected.
- Version 6.6.130, <= 6.6.* is unaffected.
- Version 6.12.78, <= 6.12.* is unaffected.
- Version 6.18.20, <= 6.18.* is unaffected.
- Version 6.19.10, <= 6.19.* is unaffected.
- Version 7.0-rc5, <= * is unaffected.