Host compromise via unchecked ISO directory length
Published Jul 28, 2026 · Updated Jul 28, 2026
Out-of-bounds reads in Xen 3.2 and later allow guest OS users using pygrub to gain host control through a malformed ISO image. The libfsimage ISO9660 directory loop trusts each attacker-controlled on-disk record length and advances without validating it. When pygrub runs de-privileged, escalation is confined to that limited context; normal execution exposes the domain construction tools and usually the host.
Summary
What happened
Out-of-bounds reads in Xen 3.2 and later allow guest OS users using pygrub to gain host control through a malformed ISO image. The libfsimage ISO9660 directory loop trusts each attacker-controlled on-disk record length and advances without validating it. When pygrub runs de-privileged, escalation is confined to that limited context; normal execution exposes the domain construction tools and usually the host.
The record
- CVE
- CVE-2026-42494
- Published
- Jul 28, 2026
- Updated
- Jul 28, 2026
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-125, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 28, 2026CVE publishedPublication date reported by the CVE source.
- Jul 28, 2026Record updatedLatest update available in the CVE record.
Exploitability
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What is affected?
Affected products and versions are unavailable in this record.
Published CVSS scores
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Attacks
What attackers are doing with it
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Public exploit references
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Technologies
Your stack
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Your stack
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