Linux Kernel up to 6.1.145/6.6.98/6.12.38/6.15.6 btrfs free-space-tree.c btrfs_search_slot_for_read allocation of resources

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4.9$0-$5k0.00

Summaryinfo

A vulnerability identified as problematic has been detected in Linux Kernel up to 6.1.145/6.6.98/6.12.38/6.15.6. The impacted element is the function btrfs_search_slot_for_read of the file fs/btrfs/free-space-tree.c of the component btrfs. This manipulation causes allocation of resources. This vulnerability is handled as CVE-2025-38503. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.1.145/6.6.98/6.12.38/6.15.6. It has been declared as problematic. Affected by this vulnerability is the function btrfs_search_slot_for_read of the file fs/btrfs/free-space-tree.c of the component btrfs. The manipulation with an unknown input leads to a allocation of resources vulnerability. The CWE definition for the vulnerability is CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. The impact remains unknown. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix assertion when building free space tree When building the free space tree with the block group tree feature enabled, we can hit an assertion failure like this: BTRFS info (device loop0 state M): rebuilding free space tree assertion failed: ret == 0, in fs/btrfs/free-space-tree.c:1102 ------------[ cut here ]------------ kernel BUG at fs/btrfs/free-space-tree.c:1102! Internal error: Oops - BUG: 00000000f2000800 [#1] SMP Modules linked in: CPU: 1 UID: 0 PID: 6592 Comm: syz-executor322 Not tainted 6.15.0-rc7-syzkaller-gd7fa1af5b33e #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : populate_free_space_tree+0x514/0x518 fs/btrfs/free-space-tree.c:1102 lr : populate_free_space_tree+0x514/0x518 fs/btrfs/free-space-tree.c:1102 sp : ffff8000a4ce7600 x29: ffff8000a4ce76e0 x28: ffff0000c9bc6000 x27: ffff0000ddfff3d8 x26: ffff0000ddfff378 x25: dfff800000000000 x24: 0000000000000001 x23: ffff8000a4ce7660 x22: ffff70001499cecc x21: ffff0000e1d8c160 x20: ffff0000e1cb7800 x19: ffff0000e1d8c0b0 x18: 00000000ffffffff x17: ffff800092f39000 x16: ffff80008ad27e48 x15: ffff700011e740c0 x14: 1ffff00011e740c0 x13: 0000000000000004 x12: ffffffffffffffff x11: ffff700011e740c0 x10: 0000000000ff0100 x9 : 94ef24f55d2dbc00 x8 : 94ef24f55d2dbc00 x7 : 0000000000000001 x6 : 0000000000000001 x5 : ffff8000a4ce6f98 x4 : ffff80008f415ba0 x3 : ffff800080548ef0 x2 : 0000000000000000 x1 : 0000000100000000 x0 : 000000000000003e Call trace: populate_free_space_tree+0x514/0x518 fs/btrfs/free-space-tree.c:1102 (P) btrfs_rebuild_free_space_tree+0x14c/0x54c fs/btrfs/free-space-tree.c:1337 btrfs_start_pre_rw_mount+0xa78/0xe10 fs/btrfs/disk-io.c:3074 btrfs_remount_rw fs/btrfs/super.c:1319 [inline] btrfs_reconfigure+0x828/0x2418 fs/btrfs/super.c:1543 reconfigure_super+0x1d4/0x6f0 fs/super.c:1083 do_remount fs/namespace.c:3365 [inline] path_mount+0xb34/0xde0 fs/namespace.c:4200 do_mount fs/namespace.c:4221 [inline] __do_sys_mount fs/namespace.c:4432 [inline] __se_sys_mount fs/namespace.c:4409 [inline] __arm64_sys_mount+0x3e8/0x468 fs/namespace.c:4409 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767 el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 Code: f0047182 91178042 528089c3 9771d47b (d4210000) ---[ end trace 0000000000000000 ]--- This happens because we are processing an empty block group, which has no extents allocated from it, there are no items for this block group, including the block group item since block group items are stored in a dedicated tree when using the block group tree feature. It also means this is the block group with the highest start offset, so there are no higher keys in the extent root, hence btrfs_search_slot_for_read() returns 1 (no higher key found). Fix this by asserting 'ret' is 0 only if the block group tree feature is not enabled, in which case we should find a block group item for the block group since it's stored in the extent root and block group item keys are greater than extent item keys (the value for BTRFS_BLOCK_GROUP_ITEM_KEY is 192 and for BTRFS_EXTENT_ITEM_KEY and BTRFS_METADATA_ITEM_KEY the values are 168 and 169 respectively). In case 'ret' is 1, we just need to add a record to the free space tree which spans the whole block group, and we can achieve this by making 'ret == 0' as the while loop's condition.

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2025-38503 since 04/16/2025. The exploitation appears to be difficult. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 259989 (Linux Distros Unpatched Vulnerability : CVE-2025-38503), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.1.146, 6.6.99, 6.12.39 or 6.15.7 eliminates this vulnerability. Applying the patch 7c77df23324f60bcff0ea44392e2c82e9486640c/f4428b2d4c68732653e93f748f538bdee639ff80/0bcc14f36c7ad37121cf5c0ae18cdde5bfad9c4e/6bbe6530b1db7b4365ce9e86144c18c5d73b2c5b/1961d20f6fa8903266ed9bd77c691924c22c8f02 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 databases at Tenable (259989), EUVD (EUVD-2025-25095) and CERT Bund (WID-SEC-2025-1858). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

  • Debian Linux
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • RESF Rocky Linux
  • Dell Avamar
  • Open Source Linux Kernel
  • Dell NetWorker
  • Dell Secure Connect Gateway
  • IBM QRadar SIEM
  • IBM Security Verify Access

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.0
VulDB Meta Temp Score: 4.9

VulDB Base Score: 4.6
VulDB Temp Score: 4.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔒

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Allocation of resources
CWE: CWE-770 / CWE-400 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 259989
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2025-38503

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.1.146/6.6.99/6.12.39/6.15.7
Patch: 7c77df23324f60bcff0ea44392e2c82e9486640c/f4428b2d4c68732653e93f748f538bdee639ff80/0bcc14f36c7ad37121cf5c0ae18cdde5bfad9c4e/6bbe6530b1db7b4365ce9e86144c18c5d73b2c5b/1961d20f6fa8903266ed9bd77c691924c22c8f02

Timelineinfo

04/16/2025 CVE reserved
08/16/2025 +122 days Advisory disclosed
08/16/2025 +0 days VulDB entry created
01/30/2026 +167 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-38503 (🔒)
GCVE (CVE): GCVE-0-2025-38503
GCVE (VulDB): GCVE-100-320371
EUVD: 🔒
CERT Bund: WID-SEC-2025-1858 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 08/16/2025 13:31
Updated: 01/30/2026 16:39
Changes: 08/16/2025 13:31 (59), 08/16/2025 17:23 (1), 08/19/2025 08:59 (1), 09/01/2025 06:31 (2), 09/28/2025 06:40 (7), 10/02/2025 18:14 (1), 10/12/2025 16:40 (1), 11/01/2025 18:43 (1), 11/18/2025 10:37 (1), 01/23/2026 03:19 (11), 01/30/2026 16:39 (1)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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