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CVE Record

CVE-2024-37356: tcp: Fix shift-out-of-bounds in dctcp_update_alpha().

In the Linux kernel, the following vulnerability has been resolved: tcp: Fix shift-out-of-bounds in dctcp_update_alpha(). In dctcp_update_alpha(), we use a module parameter dctcp_shift_g as follows: alpha -= min_not_zero(alpha, alpha >> dctcp_shift_g); ... delivered_ce <<= (10 - dctcp_shift_g); It seems syzkaller started fuzzing module parameters and triggered shift-out-of-bounds [0] by setting 100 to dctcp_shift_g: memcpy((void*)0x20000080, "/sys/module/tcp_dctcp/parameters/dctcp_shift_g\000", 47); res = syscall(__NR_openat, /*fd=*/0xffffffffffffff9cul, /*file=*/0x20000080ul, /*flags=*/2ul, /*mode=*/0ul); memcpy((void*)0x20000000, "100\000", 4); syscall(__NR_write, /*fd=*/r[0], /*val=*/0x20000000ul, /*len=*/4ul); Let's limit the max value of dctcp_shift_g by param_set_uint_minmax(). With this patch: # echo 10 > /sys/module/tcp_dctcp/parameters/dctcp_shift_g # cat /sys/module/tcp_dctcp/parameters/dctcp_shift_g 10 # echo 11 > /sys/module/tcp_dctcp/parameters/dctcp_shift_g -bash: echo: write error: Invalid argument [0]: UBSAN: shift-out-of-bounds in net/ipv4/tcp_dctcp.c:143:12 shift exponent 100 is too large for 32-bit type 'u32' (aka 'unsigned int') CPU: 0 PID: 8083 Comm: syz-executor345 Not tainted 6.9.0-05151-g1b294a1f3561 #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x201/0x300 lib/dump_stack.c:114 ubsan_epilogue lib/ubsan.c:231 [inline] __ubsan_handle_shift_out_of_bounds+0x346/0x3a0 lib/ubsan.c:468 dctcp_update_alpha+0x540/0x570 net/ipv4/tcp_dctcp.c:143 tcp_in_ack_event net/ipv4/tcp_input.c:3802 [inline] tcp_ack+0x17b1/0x3bc0 net/ipv4/tcp_input.c:3948 tcp_rcv_state_process+0x57a/0x2290 net/ipv4/tcp_input.c:6711 tcp_v4_do_rcv+0x764/0xc40 net/ipv4/tcp_ipv4.c:1937 sk_backlog_rcv include/net/sock.h:1106 [inline] __release_sock+0x20f/0x350 net/core/sock.c:2983 release_sock+0x61/0x1f0 net/core/sock.c:3549 mptcp_subflow_shutdown+0x3d0/0x620 net/mptcp/protocol.c:2907 mptcp_check_send_data_fin+0x225/0x410 net/mptcp/protocol.c:2976 __mptcp_close+0x238/0xad0 net/mptcp/protocol.c:3072 mptcp_close+0x2a/0x1a0 net/mptcp/protocol.c:3127 inet_release+0x190/0x1f0 net/ipv4/af_inet.c:437 __sock_release net/socket.c:659 [inline] sock_close+0xc0/0x240 net/socket.c:1421 __fput+0x41b/0x890 fs/file_table.c:422 task_work_run+0x23b/0x300 kernel/task_work.c:180 exit_task_work include/linux/task_work.h:38 [inline] do_exit+0x9c8/0x2540 kernel/exit.c:878 do_group_exit+0x201/0x2b0 kernel/exit.c:1027 __do_sys_exit_group kernel/exit.c:1038 [inline] __se_sys_exit_group kernel/exit.c:1036 [inline] __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xe4/0x240 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x67/0x6f RIP: 0033:0x7f6c2b5005b6 Code: Unable to access opcode bytes at 0x7f6c2b50058c. RSP: 002b:00007ffe883eb948 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 00007f6c2b5862f0 RCX: 00007f6c2b5005b6 RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001 RBP: 0000000000000001 R08: 00000000000000e7 R09: ffffffffffffffc0 R10: 0000000000000006 R11: 0000000000000246 R12: 00007f6c2b5862f0 R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001 </TASK>

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

Linux fixed a kernel bug where an unsafe tcp_dctcp module parameter could make DCTCP congestion-control code perform an invalid bit shift. The public report shows syzkaller fuzzing found it and the fix rejects out-of-range values. Treat this mainly as a kernel stability and hygiene issue unless vendor guidance says your product has higher exposure.

Executive priority

Handle in normal kernel patch governance, with higher urgency for appliances, industrial systems, or multi-tenant Linux environments that expose privileged configuration surfaces. There is no sourced evidence of active exploitation, but kernel correctness bugs should not remain unpatched across production fleets.

Technical view

dctcp_update_alpha() used dctcp_shift_g in right and left shifts without bounding the sysfs module parameter. Setting it above the expected range could cause a shift-out-of-bounds in net/ipv4/tcp_dctcp.c. Stable fixes add param_set_uint_minmax() so values above 10 are rejected. The bundle identifies multiple Linux stable branches as affected or fixed.

Likely exposure

Exposure is most plausible on Linux systems running affected kernels where tcp_dctcp is present and its module parameter can be changed. The provided evidence demonstrates local parameter manipulation through sysfs, not remote exploitation. Products incorporating affected Linux kernels may depend on vendor backports and advisories.

Exploitation context

No active exploitation is stated in the provided sources, and the CVE is not marked KEV. The public evidence is a syzkaller finding with a reproducer-like trace, not evidence of real-world abuse. Practical impact is unclear from the bundle beyond kernel undefined behavior and potential stability risk.

Researcher notes

The key condition is an out-of-range dctcp_shift_g value influencing shifts in dctcp_update_alpha(). The fix constrains the parameter to 0 through 10. The bundle does not provide CVSS, CWE, exploit maturity, or a complete affected product matrix beyond Linux and selected vendor advisories.

Mitigation direction

  • Apply Linux stable kernel fixes or vendor kernel updates covering CVE-2024-37356.
  • Check product advisories from your Linux distribution or device vendor.
  • Prioritize systems where tcp_dctcp is loaded or configurable by administrators.
  • Restrict privileged access to kernel module parameters according to existing hardening policy.

Validation and detection

  • Inventory Linux kernel versions against the affected and fixed branch guidance.
  • Confirm whether tcp_dctcp is present or loaded on relevant systems.
  • Verify vendor kernels include the dctcp_shift_g bounds-checking fix.
  • Check whether Siemens or Debian advisories apply to deployed products.
Prepared
Confidence
high
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
3ADP providers
13Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container
siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxe3118e8359bb7c59555aca60c725106e6d78c5ce, e3118e8359bb7c59555aca60c725106e6d78c5ce, e3118e8359bb7c59555aca60c725106e6d78c5ce, e3118e8359bb7c59555aca60c725106e6d78c5ce, e3118e8359bb7c59555aca60c725106e6d78c5ce, e3118e8359bb7c59555aca60c725106e6d78c5ce, e3118e8359bb7c59555aca60c725106e6d78c5ce, e3118e8359bb7c59555aca60c725106e6d78c5ceunaffected
LinuxLinux3.18, 0, 4.19.316, 5.4.278, 5.10.219, 5.15.161, 6.1.93, 6.6.33, 6.9.4, 6.10affected
Weakness

CWE details

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