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Loop with Unreachable Exit Condition ('Infinite Loop') Affecting kernel6.18-tools-devel package, versions <1:6.18.41-94.142.amzn2023

Severity

 Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.21% (12th percentile)

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  • Snyk IDSNYK-AMZN2023-KERNEL618TOOLSDEVEL-19466119
  • published1 Sept 2026
  • disclosed15 Aug 2026
Report a new vulnerability Found a mistake?

Introduced: 15 Aug 2026

NewCVE-2026-72193  (opens in a new tab)
CWE-835  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 kernel6.18-tools-devel to version 1:6.18.41-94.142.amzn2023 or higher.
This issue was patched in ALAS2023-2026-2071.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel6.18-tools-devel package and not the kernel6.18-tools-devel package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

ntfs3: cap RESTART_TABLE free-chain walker at rt->used

A crafted NTFS3 disk image triggers an in-kernel infinite loop at mount time, hanging the mounting thread and firing the soft-lockup watchdog within ~22s on multi-CPU hosts (panic with kernel.softlockup_panic=1). The bug is reachable from desktop USB auto-mount on distributions where udisks2 routes the NTFS signature to the in-tree ntfs3 driver (Arch family and an increasing fraction of Fedora / openSUSE / RHEL deployments); CAP_SYS_ADMIN-class manual mount elsewhere.

check_rstbl()'s second walker iterates the free-entry singly-linked list headed by rt->first_free with no upper bound on iteration count:

for (off = ff; off;) { if (off == RESTART_ENTRY_ALLOCATED) return false; off = le32_to_cpu(*(__le32 *)Add2Ptr(rt, off)); if (off > ts - sizeof(__le32)) return false; }

The existing guards cover three exits: end-of-list (off == 0), the in-use marker (off == RESTART_ENTRY_ALLOCATED), and out-of-bounds (off > ts - sizeof(__le32)). None of the three prevents an in-bounds cycle.

A crafted on-disk RESTART_TABLE whose free chain contains a self-loop or A->B->A cycle whose offsets satisfy:

  • in range [sizeof(struct RESTART_TABLE), ts - sizeof(__le32)]
  • (off - sizeof(struct RESTART_TABLE)) % rsize == 0

passes all existing guards and spins the mount-time thread forever. Reproduced in UML by hand-forging a 2 MB NTFS3 image whose journal RESTART_TABLE first_free = 0x18 and whose entry at offset 0x18 stores 0x18 as its next pointer; mount of the forged image with the in-tree ntfs3 driver never returns.

Bound the walker by rt->used. Each entry on a legitimate free chain is unique, and the total slot count is ne = le16_to_cpu (rt->used). A traversal that visits more than ne slots is by construction malformed; reject it as a corrupt RESTART_TABLE.

After this patch, mount of the forged image returns with -EINVAL and a log_replay failure message, and mkntfs-produced legitimate images mount cleanly (verified in the same UML harness).

CVSS Base Scores

version 3.1