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CVE-2026-53174
ovl: keep err zero after successful ovl_cache_get()
Published 2026-06-25 (4 months ago) by the Linux kernel CNA. Subsystem fs/overlayfs. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-53174 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
ovl_iterate_merged() stores PTR_ERR(cache) in err before checking IS_ERR(cache). On success err holds the truncated cache pointer and can be returned as a bogus non-zero error. The syzbot reproducer reaches this through overlay-on-overlay readdir: getdents64 iterate_dir(outer overlay file) ovl_iterate_merged() ovl_cache_get() ovl_dir_read_merged() ovl_dir_read() iterate_dir(inner overlay file) ovl_iterate_merged() Only compute PTR_ERR(cache) on the error path.
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/overlayfs/readdir.c
- What this is
- OVERLAY FILESYSTEMMAINTAINERS section matched on fs/overlayfs/ · linux-unionfs@vger.kernel.org · Supported
- Kernel module
- overlay
Check it on the machine
grep -w CONFIG_OVERLAY_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 overlayPrints 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 as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sidm
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_OVERLAY_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
- 2026-06-25 (4 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
- 0.17%, higher than 5.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- fs/overlayfs
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.19 | 7.0.13 | e7051909a01b |
| 6.19 | 7.1 | 1711b6ed6953 |
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 path is reached through local filesystem syscalls, specifically opening/enumerating nested overlayfs directories with getdents/getdents64. It is not reachable from network packets or adjacent/physical input.
- AC:LAttack complexity, low
- The attacker controls the overlay-on-overlay setup and the readdir/getdents trigger, and syzbot demonstrated reproducible crashes. Any pointer-value dependency can be retried or influenced with local heap grooming, so no uncontrollable race or victim state is required.
- PR:LPrivileges required, low
- Creating the crafted overlayfs setup requires local privileges, but overlayfs is marked FS_USERNS_MOUNT and is reachable in a user namespace on systems allowing unprivileged user namespaces. Thus a basic local user is sufficient in the highest reasonable deployment scenario.
- UI:NUser interaction, none
- No victim action is needed once the attacker has local execution; the attacker mounts/prepares the nested overlay and invokes getdents directly. The vulnerable code runs synchronously in the attacker's syscall path.
- S:UScope, unchanged
- The impact remains within the kernel and the local system security authority. This is not a VM escape, IOMMU bypass, or cross-scope boundary violation.
- C:HConfidentiality impact, high
- The bug can convert a successful overlay directory-cache pointer into a bogus cache pointer and produce wild memory access in ovl_seek_cursor/ovl_iterate. On severe but reasonable architectures/configurations this can amount to stale/truncated kernel-pointer use, so kernel memory disclosure is defensible.
- I:HIntegrity impact, high
- The same wild-pointer/UAF-style path can cause overlayfs to interpret invalid or attacker-influenced memory as ovl_cache_entry state and perform cache-entry updates through it. Given the kernel memory corruption primitive and uncertainty, high integrity impact is the safer defensible choice.
- A:HAvailability impact, high
- The public syzbot report is a general protection fault/Oops with KASAN wild-memory-access in ovl_iterate, reachable from getdents. A local attacker can repeatedly trigger this path to crash or panic affected kernels.