UBUNTU-CVE-2026-74569: Use After Free
In the Linux kernel, the following vulnerability has been resolved: netfilter: nfconntracksip: widen NAT rewrite delta to s32 in siphelptcp() siphelptcp() 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 S16MAX while the packet stays under the 65535 enlargeskb() limit: nfnatsip() 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 ctsipgetheader() reads past the linearized skb tail. Widen diff, tdiff and the seqadjust hook to s32. Both are bounded by the 65535 byte packet limit, and the seqadj core is already s32 (nfctseqadjset() takes s32), so no previously accepted input is rejected. BUG: KASAN: use-after-free in ctsipgetheader (net/netfilter/nfconntracksip.c:464) Read of size 1 at addr ffff888010800000 by task ksoftirqd/1/25 ctsipgetheader (net/netfilter/nfconntracksip.c:464) siphelptcp (net/netfilter/nfconntracksip.c:1694) nfconfirm (net/netfilter/nfconntrackproto.c:183) nfhookslow (net/netfilter/core.c:619) ip6output (net/ipv6/ip6output.c:246) ip6forward (net/ipv6/ip6output.c:690) ipv6rcv (net/ipv6/ip6input.c:351) netifreceiveskbonecore (net/core/dev.c:6212) processbacklog (net/core/dev.c:6676) napipoll (net/core/dev.c:7735) netrxaction (net/core/dev.c:7955) handlesoftirqs (kernel/softirq.c:622) runksoftirqd (kernel/softirq.c:1076) ...
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-aws-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1117.124~20.04.1 - Upgrade
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ubuntu/linux-azure-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1123.132~20.04.1 - Upgrade
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ubuntu/linux-azure-fde-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1122.131~20.04.1 - Upgrade
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ubuntu/linux-gcp-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1118.128~20.04.1 - Upgrade
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ubuntu/linux-hwe-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-198.208~20.04.1 - Upgrade
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ubuntu/linux-ibm-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1111.115~20.04.1 - Upgrade
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ubuntu/linux-intel-iotg-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1112.118~20.04.1 - Upgrade
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ubuntu/linux-lowlatency-hwe-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-195.205~20.04.1 - Upgrade
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ubuntu/linux-oracle-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1114.120~20.04.1 - Upgrade
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ubuntu/linux-riscv-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1111.115~20.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 5.15.0-198.208 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 5.15.0-1117.124 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 5.15.0-1123.132 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 5.15.0-1122.131 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 5.15.0-1118.128 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 5.15.0-1113.119 - Upgrade
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ubuntu/linux-gkeopto a version that resolves this vulnerability.Fixed in 5.15.0-1100.108 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 5.15.0-1111.115 - Upgrade
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ubuntu/linux-intel-iotgto a version that resolves this vulnerability.Fixed in 5.15.0-1112.118 - Upgrade
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ubuntu/linux-kvmto a version that resolves this vulnerability.Fixed in 5.15.0-1109.114 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 5.15.0-195.205 - Upgrade
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ubuntu/linux-nvidiato a version that resolves this vulnerability.Fixed in 5.15.0-1112.113 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 5.15.0-1114.120 - Upgrade
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ubuntu/linux-xilinx-zynqmpto a version that resolves this vulnerability.Fixed in 5.15.0-1080.84 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 5.15.0-1101.103 - Upgrade
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ubuntu/linux-intel-iot-realtimeto a version that resolves this vulnerability.Fixed in 5.15.0-1109.111 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 5.15.0-1116.125 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1117.124+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1123.132+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-198.208+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1118.128+fips1 - Upgrade
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ubuntu/linux-nvidia-tegrato a version that resolves this vulnerability.Fixed in 6.8.0-1035.38
Event History
Frequently Asked Questions
What conditions are required to trigger the flaw?
An attacker must be able to send a TCP SIP message through the kernel's SIP connection-tracking and NAT rewrite path. The message needs enough matching URIs, such as a long Contact list, for NAT rewriting to increase its size beyond 32,767 bytes while remaining within the 65,535-byte packet limit.
Which Ubuntu kernel packages are identified as affected?
The affected software list includes ubuntu/linux, ubuntu/linux-fips, ubuntu/linux-aws, ubuntu/linux-azure, ubuntu/linux-aws-fips, ubuntu/linux-azure-fips, ubuntu/linux-gcp, and ubuntu/linux-gcp-fips.
Does exploitation require authentication or user interaction?
No. The supplied severity vector indicates network reachability, low attack complexity, no privileges required, and no user interaction.