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Fencer Vulns
high 7.8

CVE-2025-37785 json

ext4: fix OOB read when checking dotdot dir

published 2025-04-18 18 mo ago modified 2026-10-15 25 d ago also EUVD-2025-11831

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 24%
public exploits
0
none known

Summary

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

ext4: fix OOB read when checking dotdot dir

Mounting a corrupted filesystem with directory which contains '.' dir entry with rec_len == block size results in out-of-bounds read (later on, when the corrupted directory is removed).

ext4_empty_dir() assumes every ext4 directory contains at least '.' and '..' as directory entries in the first data block. It first loads the '.' dir entry, performs sanity checks by calling ext4_check_dir_entry() and then uses its rec_len member to compute the location of '..' dir entry (in ext4_next_entry). It assumes the '..' dir entry fits into the same data block.

If the rec_len of '.' is precisely one block (4KB), it slips through the sanity checks (it is considered the last directory entry in the data block) and leaves "struct ext4_dir_entry_2 *de" point exactly past the memory slot allocated to the data block. The following call to ext4_check_dir_entry() on new value of de then dereferences this pointer which results in out-of-bounds mem access.

Fix this by extending __ext4_check_dir_entry() to check for '.' dir entries that reach the end of data block. Make sure to ignore the phony dir entries for checksum (by checking name_len for non-zero).

Note: This is reported by KASAN as use-after-free in case another structure was recently freed from the slot past the bound, but it is really an OOB read.

This issue was found by syzkaller tool.

Call Trace: [ 38.594108] BUG: KASAN: slab-use-after-free in __ext4_check_dir_entry+0x67e/0x710 [ 38.594649] Read of size 2 at addr ffff88802b41a004 by task syz-executor/5375 [ 38.595158] [ 38.595288] CPU: 0 UID: 0 PID: 5375 Comm: syz-executor Not tainted 6.14.0-rc7 #1 [ 38.595298] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 38.595304] Call Trace: [ 38.595308] <TASK> [ 38.595311] dump_stack_lvl+0xa7/0xd0 [ 38.595325] print_address_description.constprop.0+0x2c/0x3f0 [ 38.595339] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595349] print_report+0xaa/0x250 [ 38.595359] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595368] ? kasan_addr_to_slab+0x9/0x90 [ 38.595378] kasan_report+0xab/0xe0 [ 38.595389] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595400] __ext4_check_dir_entry+0x67e/0x710 [ 38.595410] ext4_empty_dir+0x465/0x990 [ 38.595421] ? __pfx_ext4_empty_dir+0x10/0x10 [ 38.595432] ext4_rmdir.part.0+0x29a/0xd10 [ 38.595441] ? __dquot_initialize+0x2a7/0xbf0 [ 38.595455] ? __pfx_ext4_rmdir.part.0+0x10/0x10 [ 38.595464] ? __pfx___dquot_initialize+0x10/0x10 [ 38.595478] ? down_write+0xdb/0x140 [ 38.595487] ? __pfx_down_write+0x10/0x10 [ 38.595497] ext4_rmdir+0xee/0x140 [ 38.595506] vfs_rmdir+0x209/0x670 [ 38.595517] ? lookup_one_qstr_excl+0x3b/0x190 [ 38.595529] do_rmdir+0x363/0x3c0 [ 38.595537] ? __pfx_do_rmdir+0x10/0x10 [ 38.595544] ? strncpy_from_user+0x1ff/0x2e0 [ 38.595561] __x64_sys_unlinkat+0xf0/0x130 [ 38.595570] do_syscall_64+0x5b/0x180 [ 38.595583] entry_SYSCALL_64_after_hwframe+0x76/0x7e

Patch / fix

  • Linux Linux 5.4.293, 5.10.236, 5.15.180, 6.1.134, 6.6.87, 6.12.23, 6.13.11, 6.14.2, 6.15
  • linux Debian 12 6.1.135-1
  • linux Debian 14, Debian 13 6.12.25-1

debian advisories DEBIAN-CVE-2025-37785

  • linux Ubuntu 22.04 LTS 5.15.0-142.152
  • linux Ubuntu 24.04 LTS 6.8.0-85.85
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1086.93
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1040.42
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1085.94
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1041.43
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1083.89
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1037.41

ubuntu advisories UBUNTU-CVE-2025-37785

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 9 5.14.0-570.21.1.el9_6
  • rv RHEL 9 5.14.0-570.21.1.el9_6
  • perf RHEL 9 5.14.0-570.21.1.el9_6
  • rtla RHEL 9 5.14.0-570.21.1.el9_6
  • libperf RHEL 9 5.14.0-570.21.1.el9_6
  • kernel-rt RHEL 9 5.14.0-570.21.1.el9_6
  • kernel-64k RHEL 9 5.14.0-570.21.1.el9_6
  • kernel-core RHEL 9 5.14.0-570.21.1.el9_6

red hat advisories RHSA-2025:8643RHSA-2025:8374

  • kernel-rt SLE Micro 5.5 5.14.21-150500.13.100.2
  • kernel-source-rt SLE Micro 5.5 5.14.21-150500.13.100.1
  • kernel-64kb SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS, SLE High Performance Computing 15 SP4-ESPOS 5.14.21-150400.24.167.1
  • kernel-syms SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS +3 more 5.14.21-150400.24.167.1
  • kernel-source SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS +3 more 5.14.21-150400.24.167.1
  • kernel-default SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE Micro 5.4 +7 more 5.14.21-150400.24.167.1
  • kernel-zfcpdump SLES 15 SP4-LTSS, Manager Server 4.3 5.14.21-150400.24.167.1
  • kernel-obs-build SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS +1 more 5.14.21-150400.24.167.1

suse advisories SUSE-SU-2025:02321-1SUSE-SU-2025:02262-1SUSE-SU-2025:02173-1SUSE-SU-2025:01967-1SUSE-SU-2025:01964-1SUSE-SU-2025:01951-1

  • kernel AlmaLinux 9 5.14.0-570.21.1.el9_6
  • rv AlmaLinux 9 5.14.0-570.21.1.el9_6
  • perf AlmaLinux 9 5.14.0-570.21.1.el9_6
  • rtla AlmaLinux 9 5.14.0-570.21.1.el9_6
  • libperf AlmaLinux 9 5.14.0-570.21.1.el9_6
  • kernel-rt AlmaLinux 9 5.14.0-570.21.1.el9_6
  • kernel-64k AlmaLinux 9 5.14.0-570.21.1.el9_6
  • kernel-core AlmaLinux 9 5.14.0-570.21.1.el9_6

almalinux advisories ALSA-2025:8643

  • kernel Rocky Linux 9 5.14.0-570.21.1.el9_6
  • kernel Rocky Linux 10 6.12.0-55.14.1.el10_0

rocky linux advisories RLSA-2025:8643RLSA-2025:8374

  • kernel Azure Linux 3.0 6.6.92.2-1

azure linux advisories AZL-61475

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-37785 updated cvss 5.5

kernel: ext4: fix OOB read when checking dotdot dir

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    affected: workaround, no fix planned “Do not mount untrusted ext4 filesystems.”
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-570.21.1.el9_6, perf 5.14.0-570.21.1.el9_6, rtla 5.14.0-570.21.1.el9_6, python3-perf 5.14.0-570.21.1.el9_6, kernel-devel-matched 5.14.0-570.21.1.el9_6, kernel-64k-devel-matched 5.14.0-570.21.1.el9_6, +7 more
    fixed: vendor fix “Do not mount untrusted ext4 filesystems.” RHSA-2025:8643
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-55.14.1.el10_0, perf 6.12.0-55.14.1.el10_0, rtla 6.12.0-55.14.1.el10_0, python3-perf 6.12.0-55.14.1.el10_0, kernel-devel-matched 6.12.0-55.14.1.el10_0, kernel-64k-devel-matched 6.12.0-55.14.1.el10_0, +7 more
    fixed: vendor fix “Do not mount untrusted ext4 filesystems.” RHSA-2025:8374
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-570.21.1.el9_6, kernel-64k 5.14.0-570.21.1.el9_6, kernel-core 5.14.0-570.21.1.el9_6, kernel-tools 5.14.0-570.21.1.el9_6, kernel-modules 5.14.0-570.21.1.el9_6, kernel-64k-core 5.14.0-570.21.1.el9_6, +27 more
    fixed: vendor fix “Do not mount untrusted ext4 filesystems.” RHSA-2025:8643
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-55.14.1.el10_0, kernel-64k 6.12.0-55.14.1.el10_0, kernel-core 6.12.0-55.14.1.el10_0, kernel-tools 6.12.0-55.14.1.el10_0, kernel-modules 6.12.0-55.14.1.el10_0, kernel-64k-core 6.12.0-55.14.1.el10_0, +27 more
    fixed: vendor fix “Do not mount untrusted ext4 filesystems.” RHSA-2025:8374
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-570.21.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.21.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.21.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.21.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.21.1.el9_6
    fixed: vendor fix “Do not mount untrusted ext4 filesystems.” RHSA-2025:8643
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-55.14.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.14.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.14.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.14.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.14.1.el10_0
    fixed: vendor fix “Do not mount untrusted ext4 filesystems.” RHSA-2025:8374
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-570.21.1.el9_6, kernel-rt-64k 5.14.0-570.21.1.el9_6, kernel-rt-core 5.14.0-570.21.1.el9_6, kernel-rt-modules 5.14.0-570.21.1.el9_6, kernel-rt-64k-core 5.14.0-570.21.1.el9_6, kernel-rt-debug-core 5.14.0-570.21.1.el9_6, +14 more
    fixed: vendor fix “Do not mount untrusted ext4 filesystems.” RHSA-2025:8643
show 3 more
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-55.14.1.el10_0, kernel-rt-64k 6.12.0-55.14.1.el10_0, kernel-rt-core 6.12.0-55.14.1.el10_0, kernel-rt-modules 6.12.0-55.14.1.el10_0, kernel-rt-64k-core 6.12.0-55.14.1.el10_0, kernel-rt-debug-core 6.12.0-55.14.1.el10_0, +14 more
    fixed: vendor fix “Do not mount untrusted ext4 filesystems.” RHSA-2025:8374
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-570.21.1.el9_6, kernel-rt-kvm 5.14.0-570.21.1.el9_6, kernel-rt-core 5.14.0-570.21.1.el9_6, kernel-rt-modules 5.14.0-570.21.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.21.1.el9_6, kernel-rt-debug-core 5.14.0-570.21.1.el9_6, +6 more
    fixed: vendor fix “Do not mount untrusted ext4 filesystems.” RHSA-2025:8643
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-55.14.1.el10_0, kernel-rt-kvm 6.12.0-55.14.1.el10_0, kernel-rt-core 6.12.0-55.14.1.el10_0, kernel-rt-modules 6.12.0-55.14.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.14.1.el10_0, kernel-rt-debug-core 6.12.0-55.14.1.el10_0, +6 more
    fixed: vendor fix “Do not mount untrusted ext4 filesystems.” RHSA-2025:8374

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-26-295-11 updated cvss 7.8

Siemens SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.7 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.7
    affected: mitigation, no fix available

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

cisa ICSA-26-209-04 updated cvss 5.5

Siemens SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.6 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.6 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.6 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.6 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.6
    affected: mitigation, no fix available

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

0.31% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 7.1 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Affected products

  • Linux Linux
  • 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

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.