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In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_reject_ipv6: fix nf_reject_ip6_tcphdr_put() syzbot reported that nf_reject_ip6_tcphdr_put() was possibly sending garbage on the four reserved tcp bits (th->res1) Use skb_put_zero() to clear the whole TCP header, as done in nf_reject_ip_tcphdr_put() BUG: KMSAN: uninit-value in nf_reject_ip6_tcphdr_put+0x688/0x6c0 net/ipv6/netfilter/nf_reject_ipv6.c:255 nf_reject_ip6_tcphdr_put+0x688/0x6c0 net/ipv6/netfilter/nf_reject_ipv6.c:255 nf_send_reset6+0xd84/0x15b0 net/ipv6/netfilter/nf_reject_ipv6.c:344 nft_reject_inet_eval+0x3c1/0x880 net/netfilter/nft_reject_inet.c:48 expr_call_ops_eval net/netfilter/nf_tables_core.c:240 [inline] nft_do_chain+0x438/0x22a0 net/netfilter/nf_tables_core.c:288 nft_do_chain_inet+0x41a/0x4f0 net/netfilter/nft_chain_filter.c:161 nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline] nf_hook_slow+0xf4/0x400 net/netfilter/core.c:626 nf_hook include/linux/netfilter.h:269 [inline] NF_HOOK include/linux/netfilter.h:312 [inline] ipv6_rcv+0x29b/0x390 net/ipv6/ip6_input.c:310 __netif_receive_skb_one_core net/core/dev.c:5661 [inline] __netif_receive_skb+0x1da/0xa00 net/core/dev.c:5775 process_backlog+0x4ad/0xa50 net/core/dev.c:6108 __napi_poll+0xe7/0x980 net/core/dev.c:6772 napi_poll net/core/dev.c:6841 [inline] net_rx_action+0xa5a/0x19b0 net/core/dev.c:6963 handle_softirqs+0x1ce/0x800 kernel/softirq.c:554 __do_softirq+0x14/0x1a kernel/softirq.c:588 do_softirq+0x9a/0x100 kernel/softirq.c:455 __local_bh_enable_ip+0x9f/0xb0 kernel/softirq.c:382 local_bh_enable include/linux/bottom_half.h:33 [inline] rcu_read_unlock_bh include/linux/rcupdate.h:908 [inline] __dev_queue_xmit+0x2692/0x5610 net/core/dev.c:4450 dev_queue_xmit include/linux/netdevice.h:3105 [inline] neigh_resolve_output+0x9ca/0xae0 net/core/neighbour.c:1565 neigh_output include/net/neighbour.h:542 [inline] ip6_finish_output2+0x2347/0x2ba0 net/ipv6/ip6_output.c:141 __ip6_finish_output net/ipv6/ip6_output.c:215 [inline] ip6_finish_output+0xbb8/0x14b0 net/ipv6/ip6_output.c:226 NF_HOOK_COND include/linux/netfilter.h:303 [inline] ip6_output+0x356/0x620 net/ipv6/ip6_output.c:247 dst_output include/net/dst.h:450 [inline] NF_HOOK include/linux/netfilter.h:314 [inline] ip6_xmit+0x1ba6/0x25d0 net/ipv6/ip6_output.c:366 inet6_csk_xmit+0x442/0x530 net/ipv6/inet6_connection_sock.c:135 __tcp_transmit_skb+0x3b07/0x4880 net/ipv4/tcp_output.c:1466 tcp_transmit_skb net/ipv4/tcp_output.c:1484 [inline] tcp_connect+0x35b6/0x7130 net/ipv4/tcp_output.c:4143 tcp_v6_connect+0x1bcc/0x1e40 net/ipv6/tcp_ipv6.c:333 __inet_stream_connect+0x2ef/0x1730 net/ipv4/af_inet.c:679 inet_stream_connect+0x6a/0xd0 net/ipv4/af_inet.c:750 __sys_connect_file net/socket.c:2061 [inline] __sys_connect+0x606/0x690 net/socket.c:2078 __do_sys_connect net/socket.c:2088 [inline] __se_sys_connect net/socket.c:2085 [inline] __x64_sys_connect+0x91/0xe0 net/socket.c:2085 x64_sys_call+0x27a5/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:43 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f Uninit was stored to memory at: nf_reject_ip6_tcphdr_put+0x60c/0x6c0 net/ipv6/netfilter/nf_reject_ipv6.c:249 nf_send_reset6+0xd84/0x15b0 net/ipv6/netfilter/nf_reject_ipv6.c:344 nft_reject_inet_eval+0x3c1/0x880 net/netfilter/nft_reject_inet.c:48 expr_call_ops_eval net/netfilter/nf_tables_core.c:240 [inline] nft_do_chain+0x438/0x22a0 net/netfilter/nf_tables_core.c:288 nft_do_chain_inet+0x41a/0x4f0 net/netfilter/nft_chain_filter.c:161 nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline] nf_hook_slow+0xf4/0x400 net/netfilter/core.c:626 nf_hook include/linux/netfilter.h:269 [inline] NF_HOOK include/linux/netfilter.h:312 [inline] ipv6_rcv+0x29b/0x390 net/ipv6/ip6_input.c:310 __netif_receive_skb_one_core ---truncated---
CVSS 3.1 Base Score 9.1. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H).
Here, a boolean initiailized field is consulted to ensure that initialization tasks are only completed once. However, the field is mistakenly set to true during static initialization, so the initialization code is never reached.
}
initialized = true;// perform initialization tasksThe following code intends to limit certain operations to the administrator only.
}$uid = ExtractUserID($state);# do stuffDoAdminThings();If the application is unable to extract the state information - say, due to a database timeout - then the $uid variable will not be explicitly set by the programmer. This will cause $uid to be regarded as equivalent to "0" in the conditional, allowing the original user to perform administrator actions. Even if the attacker cannot directly influence the state data, unexpected errors could cause incorrect privileges to be assigned to a user just by accident.
The following code intends to concatenate a string to a variable and print the string.
printf("%s", str);This might seem innocent enough, but str was not initialized, so it contains random memory. As a result, str[0] might not contain the null terminator, so the copy might start at an offset other than 0. The consequences can vary, depending on the underlying memory.
If a null terminator is found before str[8], then some bytes of random garbage will be printed before the "hello world" string. The memory might contain sensitive information from previous uses, such as a password (which might occur as a result of CWE-14 or CWE-244). In this example, it might not be a big deal, but consider what could happen if large amounts of memory are printed out before the null terminator is found.
If a null terminator isn't found before str[8], then a buffer overflow could occur, since strcat will first look for the null terminator, then copy 12 bytes starting with that location. Alternately, a buffer over-read might occur (CWE-126) if a null terminator isn't found before the end of the memory segment is reached, leading to a segmentation fault and crash.
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