Linux Kernel up to 6.9.3 fuse fs/fuse/dev.c write memory corruption

Summaryinfo

A vulnerability classified as critical was found in Linux Kernel up to 6.9.3. This affects the function write of the file fs/fuse/dev.c of the component fuse. Executing a manipulation can lead to memory corruption. This vulnerability is tracked as CVE-2024-38626. No exploit exists. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.9.3. It has been declared as critical. This vulnerability affects the function write of the file fs/fuse/dev.c of the component fuse. The manipulation with an unknown input leads to a memory corruption vulnerability. The CWE definition for the vulnerability is CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: fuse: clear FR_SENT when re-adding requests into pending list The following warning was reported by lee bruce: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 8264 at fs/fuse/dev.c:300 fuse_request_end+0x685/0x7e0 fs/fuse/dev.c:300 Modules linked in: CPU: 0 PID: 8264 Comm: ab2 Not tainted 6.9.0-rc7 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) RIP: 0010:fuse_request_end+0x685/0x7e0 fs/fuse/dev.c:300 ...... Call Trace: fuse_dev_do_read.constprop.0+0xd36/0x1dd0 fs/fuse/dev.c:1334 fuse_dev_read+0x166/0x200 fs/fuse/dev.c:1367 call_read_iter include/linux/fs.h:2104 [inline] new_sync_read fs/read_write.c:395 [inline] vfs_read+0x85b/0xba0 fs/read_write.c:476 ksys_read+0x12f/0x260 fs/read_write.c:619 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xce/0x260 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f ...... The warning is due to the FUSE_NOTIFY_RESEND notify sent by the write() syscall in the reproducer program and it happens as follows: (1) calls fuse_dev_read() to read the INIT request The read succeeds. During the read, bit FR_SENT will be set on the request. (2) calls fuse_dev_write() to send an USE_NOTIFY_RESEND notify The resend notify will resend all processing requests, so the INIT request is moved from processing list to pending list again. (3) calls fuse_dev_read() with an invalid output address fuse_dev_read() will try to copy the same INIT request to the output address, but it will fail due to the invalid address, so the INIT request is ended and triggers the warning in fuse_request_end(). Fix it by clearing FR_SENT when re-adding requests into pending list.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2024-38626 since 06/18/2024. The exploitation appears to be easy. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 10/03/2025).

The vulnerability scanner Nessus provides a plugin with the ID 249924 (Linux Distros Unpatched Vulnerability : CVE-2024-38626), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.9.4 eliminates this vulnerability. Applying the patch 533070db659a/246014876d78 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (249924). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.9.0
• 6.9.1
• 6.9.2
• 6.9.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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