EUVD-2026-50403Severity by source
CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Local vector; high complexity due to SUID/SGID file precondition in lower layer; low-privileged local process required; integrity-only impact on file mode bits.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
Lifecycle Timeline
3DescriptionCVE.org
fuse-overlayfs is an implementation of overlayfs in FUSE for rootless containers. Prior to 1.17, the release-1.x C branch preserves SUID and SGID mode bits in main.c during open(O_TRUNC) and truncate handling on a copied-up file, allowing a low-privileged process to leave the upper-layer file with mode 4777. This issue is fixed in version 1.17.
AnalysisAI
Incorrect SUID/SGID bit preservation in fuse-overlayfs before version 1.17 allows a low-privileged process inside a rootless container to leave an upper-layer file with mode 4777 (setuid plus world-writable) by triggering a copy-up via open(O_TRUNC) or truncate. The vulnerability is confined to local container contexts and carries a CVSS 4.0 score of 2.0, reflecting narrow exploitation conditions and limited integrity-only impact. No active exploitation (KEV) or public exploit code has been identified at time of analysis.
Technical ContextAI
fuse-overlayfs is a userspace FUSE-based reimplementation of the Linux kernel OverlayFS, purpose-built to provide overlay filesystem semantics for rootless containers without requiring elevated kernel privileges. In overlay filesystems, modifying a file from the read-only lower layer triggers a 'copy-up' to the writable upper layer. CWE-266 (Incorrect Privilege Assignment) identifies the root cause: the C implementation in main.c omitted the mandatory clearing of SUID (S_ISUID) and SGID (S_ISGID) mode bits when a copied-up file was opened with O_TRUNC or subjected to a truncate operation. POSIX and standard kernel OverlayFS both require these bits to be stripped during such operations for unprivileged callers. The fix, introduced in commit 97e0d968a782fc259ebde112db1e9b9ff1ad724f, adds a clear_suid_sgid() helper that is invoked in both the ovl_open() O_TRUNC path and the ovl_setattr() truncation path in main.c. The affected CPE is cpe:2.3:a:containers:fuse-overlayfs:*:*:*:*:*:*:*:*.
RemediationAI
Upgrade fuse-overlayfs to version 1.17 or later. The patched release is available at https://github.com/containers/fuse-overlayfs/releases/tag/v1.17, and the specific fixing commit is https://github.com/containers/fuse-overlayfs/commit/97e0d968a782fc259ebde112db1e9b9ff1ad724f. If an immediate upgrade is not feasible, the most targeted compensating control is to avoid including SUID- or SGID-marked binaries in container image layers deployed via fuse-overlayfs; this eliminates the copy-up precondition entirely at the cost of disabling setuid functionality within those containers. No network-level blocking or ACL change can mitigate this issue, as the attack vector is local and filesystem-based.
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Same weakness CWE-266 – Incorrect Privilege Assignment
View allSame technique Information Disclosure
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External POC / Exploit Code
Leaving vuln.today