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

2026-10-14T22:20:33.525090+00:00

Affected: Linux, Siemens RUGGEDCOM RST2428P, Siemens SCALANCE XC-300/XR-300/XC-400/XR-500WG/XR-500 family, Siemens SCALANCE XCM-/XRM-/XCH-/XRH-300 family, Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem, Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP, Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP, Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

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: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x201/0x300 lib/dump_stack…

USN-6951-1 — linux, linux-aws, linux-aws-5.4, linux-gcp, linux-gcp-5.4, linux-gkeop, linux-hwe-5.4, linux-ibm, linux-ibm-5.4, linux-…

2026-10-14T22:20:33.525206+00:00

Affected: Ubuntu:Pro:18.04:LTS: linux-aws-5.4, Ubuntu:Pro:18.04:LTS: linux-gcp-5.4, Ubuntu:Pro:18.04:LTS: linux-hwe-5.4, Ubuntu:Pro:18.04:LTS: linux-ibm-5.4, Ubuntu:20.04:LTS: linux, Ubuntu:20.04:LTS: linux-aws, Ubuntu:20.04:LTS: linux-gcp, Ubuntu:20.04:LTS: linux-gkeop, Ubuntu:20.04:LTS: linux-ibm, Ubuntu:20.04:LTS: linux-iot and 3 more

Several security issues were discovered in the Linux kernel. An attacker could possibly use these to compromise the system. This update corrects flaws in the following subsystems: - ARM64 architecture; - M68K architecture; - User-Mode Linux (UML); - x86 architecture; - Accessibility subsystem; - Character device driver; - Clock framework and drivers; - CPU frequency scaling framework; - Hardware crypto device drivers; - Buffer Sharing and Synchronization framework; - FireWire subsystem; - GPU drivers; - HW tracing; - Macintosh device drivers; - Multiple devices driver; - Media drivers; - Network drivers; - Pin controllers subsystem; - S/390 drivers; - SCSI drivers; - SoundWire subsystem; - Greybus lights staging drivers; - TTY drivers; - Framebuffer layer; - Virtio drivers; - 9P distributed file system; - eCrypt file system; - EROFS file system; - Ext4 file system; - F2FS file system; - JFFS2 file system; - Network file system client; - NILFS2 file system; - SMB network file system; - Kernel debugger infrastructure; - IRQ subsystem; - Tracing infrastructure; - Dynamic debug library; - 9P file system network protocol; - Bluetooth subsystem; - Networking core; - IPv4 networking; - IPv6 networking; - Netfilter; - NET/ROM layer; - NFC subsystem; - NSH protocol; - Open vSwitch; - Phonet protocol; - TIPC protocol; - Unix domain sockets; - Wireless networking; - eXpress Data Pa…