Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: correct the order of...
In the Linux kernel, the following vulnerability has been resolved:
btrfs: correct the order of prelim_ref arguments in btrfs__prelim_ref
btrfs_prelim_ref() calls the old and new reference variables in the
incorrect order. This causes a NULL pointer dereference because oldref
is passed as NULL to trace_btrfs_prelim_ref_insert().
Note, trace_btrfs_prelim_ref_insert() is being called with newref as
oldref (and oldref as NULL) on purpose in order to print out
the values of newref.
To reproduce:
echo 1 > /sys/kernel/debug/tracing/events/btrfs/btrfs_prelim_ref_insert/enable
Perform some writeback operations.
Backtrace:
BUG: kernel NULL pointer dereference, address: 0000000000000018
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 115949067 P4D 115949067 PUD 11594a067 PMD 0
Oops: Oops: 0000 [#1] SMP NOPTI
CPU: 1 UID: 0 PID: 1188 Comm: fsstress Not tainted 6.15.0-rc2-tester+ #47 PREEMPT(voluntary) 7ca2cef72d5e9c600f0c7718adb6462de8149622
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-2-gc13ff2cd-prebuilt.qemu.org 04/01/2014
RIP: 0010:trace_event_raw_event_btrfs__prelim_ref+0x72/0x130
Code: e8 43 81 9f ff 48 85 c0 74 78 4d 85 e4 0f 84 8f 00 00 00 49 8b 94 24 c0 06 00 00 48 8b 0a 48 89 48 08 48 8b 52 08 48 89 50 10 <49> 8b 55 18 48 89 50 18 49 8b 55 20 48 89 50 20 41 0f b6 55 28 88
RSP: 0018:ffffce44820077a0 EFLAGS: 00010286
RAX: ffff8c6b403f9014 RBX: ffff8c6b55825730 RCX: 304994edf9cf506b
RDX: d8b11eb7f0fdb699 RSI: ffff8c6b403f9010 RDI: ffff8c6b403f9010
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000010
R10: 00000000ffffffff R11: 0000000000000000 R12: ffff8c6b4e8fb000
R13: 0000000000000000 R14: ffffce44820077a8 R15: ffff8c6b4abd1540
FS: 00007f4dc6813740(0000) GS:ffff8c6c1d378000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000018 CR3: 000000010eb42000 CR4: 0000000000750ef0
PKRU: 55555554
Call Trace:
prelim_ref_insert+0x1c1/0x270
find_parent_nodes+0x12a6/0x1ee0
? __entry_text_end+0x101f06/0x101f09
? srso_alias_return_thunk+0x5/0xfbef5
? srso_alias_return_thunk+0x5/0xfbef5
? srso_alias_return_thunk+0x5/0xfbef5
? srso_alias_return_thunk+0x5/0xfbef5
btrfs_is_data_extent_shared+0x167/0x640
? fiemap_process_hole+0xd0/0x2c0
extent_fiemap+0xa5c/0xbc0
? __entry_text_end+0x101f05/0x101f09
btrfs_fiemap+0x7e/0xd0
do_vfs_ioctl+0x425/0x9d0
__x64_sys_ioctl+0x75/0xc0
Impact
The application dereferences a null pointer, causing a crash. Typical impact: denial of service via crash.
CVE-2025-38034 has a CVSS score of 5.5 (Medium). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2025-38034? CVE-2025-38034 is a medium-severity null pointer dereference vulnerability. No fixed version is listed yet. The application dereferences a null pointer, causing a crash.
- How severe is CVE-2025-38034? CVE-2025-38034 has a CVSS score of 5.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Is there a fix for CVE-2025-38034? No fixed version is listed for CVE-2025-38034 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2025-38034 exploitable, and should I be worried? Whether CVE-2025-38034 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-38034 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.