CVE-2026-72193: ntfs3: cap RESTART_TABLE free-chain walker at rt->used
In the Linux kernel, the following vulnerability has been resolved:
ntfs3: cap RESTARTTABLE 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.softlockuppanic=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); CAPSYSADMIN-class manual mount elsewhere.
checkrstbl()'s second walker iterates the free-entry singly-linked list headed by rt->firstfree with no upper bound on iteration count:
for (off = ff; off;) { if (off == RESTARTENTRYALLOCATED) return false; off = le32tocpu((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 == RESTARTENTRYALLOCATED), and out-of-bounds (off > ts - sizeof(le32)). None of the three prevents an in-bounds cycle.
A crafted on-disk RESTARTTABLE whose free chain contains a self-loop or A->B->A cycle whose offsets satisfy:
- in range [sizeof(struct RESTARTTABLE), ts - sizeof(le32)] - (off - sizeof(struct RESTARTTABLE)) % 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 RESTARTTABLE firstfree = 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 = le16tocpu (rt->used). A traversal that visits more than ne slots is by construction malformed; reject it as a corrupt RESTARTTABLE.
After this patch, mount of the forged image returns with -EINVAL and a logreplay failure message, and mkntfs-produced legitimate images mount cleanly (verified in the same UML harness).
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1118.128+fips1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 6.8.0-147.147 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70 - Upgrade
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ubuntu/linux-aws-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-gcp-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 6.8.0-1066.74 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 6.8.0-1067.68 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 6.8.0-147.147.1 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 6.8.0-1064.67 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 6.8.0-1033.38 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.8.1-1062.63 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-147.147+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-38.38 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.0.0-1016.16 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1008.9 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Compensating control
In ntfs3 check_rstbl(), bound the RESTART_TABLE free-chain walker by rt->used (ne = le16_to_cpu(rt->used)); reject a traversal that visits more than ne slots as a corrupt RESTART_TABLE, causing the forged mount to return -EINVAL.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-72193?
CVE-2026-72193 has a risk score of 33, indicating it poses a significant threat to system stability.
How does CVE-2026-72193 affect Linux systems?
CVE-2026-72193 can cause an in-kernel infinite loop when mounting a crafted NTFS3 disk image, resulting in system hangs.
How do I fix CVE-2026-72193?
To mitigate CVE-2026-72193, you should apply the latest patches provided by your Linux distribution.
What systems are vulnerable to CVE-2026-72193?
CVE-2026-72193 affects Linux kernel versions that include the ntfs3 file system capabilities.
When was CVE-2026-72193 published?
CVE-2026-72193 was published on August 15, 2026.