Critical 9.8Published Aug 15, 2026

CVE-2026-74569netfilter: nf_conntrack_sip: widen NAT rewrite delta to s32 in sip_help_tcp()

Updated under an hour ago (Oct 27, 2026, 11:00 PM ET)

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In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_sip: widen NAT rewrite delta to s32 in sip_help_tcp() sip_help_tcp() stores the size change of each NAT-rewritten SIP message in s16 diff and accumulates it in s16 tdiff, but a single message can grow by more than S16_MAX while the packet stays under the 65535 enlarge_skb() limit: nf_nat_sip() rewrites every matching URI, and a long Contact list expands the message by tens of kilobytes. diff then wraps, and "datalen = datalen + diff - msglen" yields a huge unsigned datalen, so the next iteration's ct_sip_get_header() reads past the linearized skb tail. Widen diff, tdiff and the seq_adjust hook to s32. Both are bounded by the 65535 byte packet limit, and the seqadj core is already s32 (nf_ct_seqadj_set() takes s32), so no previously accepted input is rejected. BUG: KASAN: use-after-free in ct_sip_get_header (net/netfilter/nf_conntrack_sip.c:464) Read of size 1 at addr ffff888010800000 by task ksoftirqd/1/25 ct_sip_get_header (net/netfilter/nf_conntrack_sip.c:464) sip_help_tcp (net/netfilter/nf_conntrack_sip.c:1694) nf_confirm (net/netfilter/nf_conntrack_proto.c:183) nf_hook_slow (net/netfilter/core.c:619) ip6_output (net/ipv6/ip6_output.c:246) ip6_forward (net/ipv6/ip6_output.c:690) ipv6_rcv (net/ipv6/ip6_input.c:351) __netif_receive_skb_one_core (net/core/dev.c:6212) process_backlog (net/core/dev.c:6676) __napi_poll (net/core/dev.c:7735) net_rx_action (net/core/dev.c:7955) handle_softirqs (kernel/softirq.c:622) run_ksoftirqd (kernel/softirq.c:1076) ...

CVSS: 9.8 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Received
Record last updated: Oct 16, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from f5b321bd37fbec9188feb1f721ab46a5ac0b35da before ed1f9be6dc8e2e280b8725e44ccdc6e0cd38640d; from f5b321bd37fbec9188feb1f721ab46a5ac0b35da before 1b0843f9e9b9b0b9b4b70d143b67e58163c85b2c; from f5b321bd37fbec9188feb1f721ab46a5ac0b35da before 32d4abc8923b0d4046fd63ad6e4917872e44eb6d; from f5b321bd37fbec9188feb1f721ab46a5ac0b35da before 63eea41759fd682229c14e0a2205802b46d106f3; from f5b321bd37fbec9188feb1f721ab46a5ac0b35da before c97621a110e386b2dd69e276eb699e1d3cec581d; from f5b321bd37fbec9188feb1f721ab46a5ac0b35da before f74554e67ccf04d1fa71069e8c9afa2717e40716; from f5b321bd37fbec9188feb1f721ab46a5ac0b35da before ef5e2c6555d2bb52dfe0e4053a8c6193f9d83b64; from f5b321bd37fbec9188feb1f721ab46a5ac0b35da before db3d0e0e5d4bc5ab4fe445b9f413d1b486508ca5	CNA record

References

References

https://git.kernel.org/stable/c/ed1f9be6dc8e2e280b8725e44ccdc6e0cd38640d
https://git.kernel.org/stable/c/1b0843f9e9b9b0b9b4b70d143b67e58163c85b2c
https://git.kernel.org/stable/c/32d4abc8923b0d4046fd63ad6e4917872e44eb6d
https://git.kernel.org/stable/c/63eea41759fd682229c14e0a2205802b46d106f3
https://git.kernel.org/stable/c/c97621a110e386b2dd69e276eb699e1d3cec581d
https://git.kernel.org/stable/c/f74554e67ccf04d1fa71069e8c9afa2717e40716
https://git.kernel.org/stable/c/ef5e2c6555d2bb52dfe0e4053a8c6193f9d83b64
https://git.kernel.org/stable/c/db3d0e0e5d4bc5ab4fe445b9f413d1b486508ca5

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.