CVE-2024-26815 in Linux
Summary
by MITRE • 04/10/2024
In the Linux kernel, the following vulnerability has been resolved:
net/sched: taprio: proper TCA_TAPRIO_TC_ENTRY_INDEX check
taprio_parse_tc_entry() is not correctly checking TCA_TAPRIO_TC_ENTRY_INDEX attribute:
int tc; // Signed value
tc = nla_get_u32(tb[TCA_TAPRIO_TC_ENTRY_INDEX]);
if (tc >= TC_QOPT_MAX_QUEUE) {
NL_SET_ERR_MSG_MOD(extack, "TC entry index out of range"); return -ERANGE; }
syzbot reported that it could fed arbitary negative values:
UBSAN: shift-out-of-bounds in net/sched/sch_taprio.c:1722:18 shift exponent -2147418108 is negative CPU: 0 PID: 5066 Comm: syz-executor367 Not tainted 6.8.0-rc7-syzkaller-00136-gc8a5c731fd12 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024 Call Trace: __dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106 ubsan_epilogue lib/ubsan.c:217 [inline]
__ubsan_handle_shift_out_of_bounds+0x3c7/0x420 lib/ubsan.c:386 taprio_parse_tc_entry net/sched/sch_taprio.c:1722 [inline]
taprio_parse_tc_entries net/sched/sch_taprio.c:1768 [inline]
taprio_change+0xb87/0x57d0 net/sched/sch_taprio.c:1877 taprio_init+0x9da/0xc80 net/sched/sch_taprio.c:2134 qdisc_create+0x9d4/0x1190 net/sched/sch_api.c:1355 tc_modify_qdisc+0xa26/0x1e40 net/sched/sch_api.c:1776 rtnetlink_rcv_msg+0x885/0x1040 net/core/rtnetlink.c:6617 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2543 netlink_unicast_kernel net/netlink/af_netlink.c:1341 [inline]
netlink_unicast+0x7ea/0x980 net/netlink/af_netlink.c:1367 netlink_sendmsg+0xa3b/0xd70 net/netlink/af_netlink.c:1908 sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg+0x221/0x270 net/socket.c:745 ____sys_sendmsg+0x525/0x7d0 net/socket.c:2584 ___sys_sendmsg net/socket.c:2638 [inline]
__sys_sendmsg+0x2b0/0x3a0 net/socket.c:2667 do_syscall_64+0xf9/0x240 entry_SYSCALL_64_after_hwframe+0x6f/0x77 RIP: 0033:0x7f1b2dea3759 Code: 48 83 c4 28 c3 e8 d7 19 00 00 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffd4de452f8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f1b2def0390 RCX: 00007f1b2dea3759 RDX: 0000000000000000 RSI: 00000000200007c0 RDI: 0000000000000004 RBP: 0000000000000003 R08: 0000555500000000 R09: 0000555500000000 R10: 0000555500000000 R11: 0000000000000246 R12: 00007ffd4de45340 R13: 00007ffd4de45310 R14: 0000000000000001 R15: 00007ffd4de45340
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Analysis
by VulDB Data Team • 12/04/2025
The vulnerability described in CVE-2024-26815 resides within the Linux kernel's Traffic Control subsystem, specifically in the taprio (Time Aware Round Robin) queuing discipline implementation. This flaw manifests in the `taprio_parse_tc_entry()` function where an improper validation of the `TCA_TAPRIO_TC_ENTRY_INDEX` attribute allows for arbitrary negative values to be processed. The issue stems from a type casting operation where a signed integer variable `tc` is assigned the value of an unsigned 32-bit attribute without proper bounds checking for negative values. When negative values are passed, they are interpreted as large positive values due to two's complement representation, leading to out-of-bounds memory access and potential kernel memory corruption. The UBSAN (Undefined Behavior Sanitizer) report indicates a shift-out-of-bounds error occurring at line 1722 in the `sch_taprio.c` file, where the negative shift exponent triggers undefined behavior.
The operational impact of this vulnerability is significant as it can be exploited to cause kernel crashes or potentially enable privilege escalation depending on the specific memory corruption patterns. Attackers could leverage this issue by crafting malicious netlink messages that contain negative values for the TC entry index attribute, which would bypass the intended range validation. This vulnerability aligns with CWE-129, which describes improper validation of array index bounds, and can be categorized under ATT&CK technique T1068, which involves exploiting privileges to escalate access. The vulnerability's exploitation path involves manipulating kernel data structures through the netlink interface, specifically targeting the Traffic Control API that allows configuration of queuing disciplines.
Mitigation strategies should focus on implementing robust input validation that explicitly checks for negative values before casting unsigned attributes to signed integers. The fix requires modifying the validation logic to ensure that the `tc` variable is properly constrained to valid queue index ranges, including checking for negative values that could result from improper attribute handling. System administrators should ensure that all kernel updates are applied promptly to address this vulnerability. Additionally, monitoring for unusual network traffic patterns or kernel memory access violations may help detect exploitation attempts. Organizations should also consider implementing network segmentation and access controls to limit potential attack surface exposure, particularly in environments where untrusted users might have access to network configuration interfaces. The vulnerability underscores the importance of proper signedness handling in kernel code and demonstrates how seemingly minor input validation gaps can lead to serious security implications.