CVE-2025-21845 mtd: spi-nor: sst: Fix SST write failure

What is CVE-2025-21845?

CVE-2025-21845 is a medium-severity denial of service vulnerability in Linux kernel, published on 12 Mar 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

mtd: spi-nor: sst: Fix SST write failure

'commit 18bcb4aa54ea ("mtd: spi-nor: sst: Factor out common write operation to `sst_nor_write_data()`")' introduced a bug where only one byte of data is written, regardless of the number of bytes passed to sst_nor_write_data(), causing a kernel crash during the write operation. Ensure the correct number of bytes are written as passed to sst_nor_write_data().

Call trace: [ 57.400180] ------------[ cut here ]------------ [ 57.404842] While writing 2 byte written 1 bytes [ 57.409493] WARNING: CPU: 0 PID: 737 at drivers/mtd/spi-nor/sst.c:187 sst_nor_write_data+0x6c/0x74 [ 57.418464] Modules linked in: [ 57.421517] CPU: 0 UID: 0 PID: 737 Comm: mtd_debug Not tainted 6.12.0-g5ad04afd91f9 #30 [ 57.429517] Hardware name: Xilinx Versal A2197 Processor board revA - x-prc-02 revA (DT) [ 57.437600] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 57.444557] pc : sst_nor_write_data+0x6c/0x74 [ 57.448911] lr : sst_nor_write_data+0x6c/0x74 [ 57.453264] sp : ffff80008232bb40 [ 57.456570] x29: ffff80008232bb40 x28: 0000000000010000 x27: 0000000000000001 [ 57.463708] x26: 000000000000ffff x25: 0000000000000000 x24: 0000000000000000 [ 57.470843] x23: 0000000000010000 x22: ffff80008232bbf0 x21: ffff000816230000 [ 57.477978] x20: ffff0008056c0080 x19: 0000000000000002 x18: 0000000000000006 [ 57.485112] x17: 0000000000000000 x16: 0000000000000000 x15: ffff80008232b580 [ 57.492246] x14: 0000000000000000 x13: ffff8000816d1530 x12: 00000000000004a4 [ 57.499380] x11: 000000000000018c x10: ffff8000816fd530 x9 : ffff8000816d1530 [ 57.506515] x8 : 00000000fffff7ff x7 : ffff8000816fd530 x6 : 0000000000000001 [ 57.513649] x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000 [ 57.520782] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0008049b0000 [ 57.527916] Call trace: [ 57.530354] sst_nor_write_data+0x6c/0x74 [ 57.534361] sst_nor_write+0xb4/0x18c [ 57.538019] mtd_write_oob_std+0x7c/0x88 [ 57.541941] mtd_write_oob+0x70/0xbc [ 57.545511] mtd_write+0x68/0xa8 [ 57.548733] mtdchar_write+0x10c/0x290 [ 57.552477] vfs_write+0xb4/0x3a8 [ 57.555791] ksys_write+0x74/0x10c [ 57.559189] __arm64_sys_write+0x1c/0x28 [ 57.563109] invoke_syscall+0x54/0x11c [ 57.566856] el0_svc_common.constprop.0+0xc0/0xe0 [ 57.571557] do_el0_svc+0x1c/0x28 [ 57.574868] el0_svc+0x30/0xcc [ 57.577921] el0t_64_sync_handler+0x120/0x12c [ 57.582276] el0t_64_sync+0x190/0x194 [ 57.585933] ---[ end trace 0000000000000000 ]---

[[email protected]: add Cc stable tag]

Which versions are affected by CVE-2025-21845?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2025-21845?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2025-21845 being exploited?

There is no known exploitation of CVE-2025-21845 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2025-21845, DEBIAN-CVE-2025-21845, GHSA-263p-9rp6-x92j, UBUNTU-CVE-2025-21845.