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CVE-2026-64361
hfs/hfsplus: fix u32 overflow in check_and_correct_requested_length
Published 2026-07-25 (3 months ago) by the Linux kernel CNA. Subsystem fs/hfs. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-64361 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4720-1 · 2026-08-05 · text | 6.1.180-1 | Update the kernel and reboot. DLA-4720-1 shipped the fix on 2026-08-05, in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6405-1 · 2026-07-31 · text | 6.12.100-1 | Update the kernel and reboot. DSA-6405-1 shipped the fix on 2026-07-31, in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4724-1 · 2026-08-07 · text | 6.12.100-1~deb12u1 | Update the kernel and reboot. DLA-4724-1 shipped the fix on 2026-08-07, in 6.12.100-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
check_and_correct_requested_length() compares (off + len) against node_size using u32 arithmetic. When the caller passes a large len value (e.g. from an underflowed subtraction in hfs_brec_remove()), off + len can wrap past 2^32 and produce a small result, causing the bounds check to pass when it should fail. For example, with off=14 and len=0xFFFFFFF2 (underflowed from data_off - keyoffset - size in hfs_brec_remove), off + len wraps to 6, which is less than a typical node_size of 512, so the check passes and the subsequent memmove reads ~4GB past the node buffer. Fix this by widening the addition to u64 before comparing against node_size. This prevents the u32 wrap while keeping the logic straightforward.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
fs/hfs/bnode.c
fs/hfsplus/hfsplus_fs.h
- What this is
- HFS FILESYSTEMMAINTAINERS section matched on fs/hfs/ · linux-fsdevel@vger.kernel.org · Maintained
- Kernel module
- hfs
Check it on the machine
grep -w CONFIG_HFS_FS /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w hfsPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookworm, trixie, forky, sid, bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_HFS_FS
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-07-25 (3 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.13%, higher than 2.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/hfs
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.10.241 | 5.10.261 | c8dd112173c0 |
| 5.15.190 | 5.15.212 | fc9d1447ca3c |
| 6.1.149 | 6.1.178 | 671c3fcc2ad3 |
| 6.6.103 | 6.6.145 | b6a481642ea1 |
| 6.12.43 | 6.12.97 | 7399c3baee7b |
| 6.17 | 6.18.40 | 607217f7ad41 |
| 6.17 | 7.1.4 | c25d3c931a63 |
| 6.17 | 7.2 | 966cb76fb285 |
| 5.4.297 | 0 | 0 |
| 6.15.11 | 0 | 0 |
| 6.16.2 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4724-1 | 2026-08-07 | bookworm 6.12.100-1~deb12u1 | tracker |
| DLA-4723-1 | 2026-08-07 | bullseye 6.1.180-1~deb11u1 | tracker |
| DLA-4720-1 | 2026-08-05 | bookworm 6.1.180-1 | tracker |
| DLA-4717-1 | 2026-08-05 | bullseye 5.10.262-1 | tracker |
| DSA-6405-1 | 2026-07-31 | trixie 6.12.100-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The vulnerable HFS/HFS+ B-tree operations are reachable through local filesystem syscalls such as removexattr() and rename() after a crafted volume is mounted. No network protocol directly supplies the malformed B-tree metadata.
- AC:LAttack complexity, low
- A crafted B-tree deterministically produces the length underflow and u32 addition wrap; no race or condition outside the attacker's control is required.
- PR:LPrivileges required, low
- Although mounting HFS/HFS+ requires init-namespace CAP_SYS_ADMIN, an unprivileged user with ordinary write access to a file on an already mounted crafted volume can trigger the flaw through user.* xattr removal or permitted rename operations.
- UI:NUser interaction, none
- The attacker can invoke the triggering filesystem syscall directly once the crafted volume is mounted; no action by another user is required.
- S:UScope, unchanged
- The corruption occurs in the kernel while processing filesystem metadata and does not cross a separate virtualization, IOMMU, or other security authority boundary.
- C:HConfidentiality impact, high
- The wrapped near-4-GiB copy performs out-of-bounds reads and, in HFS+, can walk beyond the node's page-pointer array, providing a defensible path to broad kernel-memory disclosure.
- I:HIntegrity impact, high
- The affected move, copy, clear, and write paths can write beyond the B-tree node buffer; the huge memmove is therefore exploitable memory corruption rather than a read-only crash.
- A:HAvailability impact, high
- The enormous out-of-bounds memory operation can reliably cause a kernel oops or panic and can corrupt large regions of kernel memory, producing complete system unavailability.