RHSA-2026:5396
Vulnerability from csaf_redhat - Published: 2026-03-23 13:14 - Updated: 2026-04-19 19:41Summary
Red Hat Security Advisory: Red Hat Hardened Images RPM Release
Severity
Important
Notes
Topic: Red Hat Hardened Images RPM Release
Details: Red Hat Hardened Images RPM Release
Terms of Use: This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.
A memory amplification vulnerability in libexpat allows attackers to trigger excessive dynamic memory allocations by submitting specially crafted XML input. A small input (~250 KiB) can cause the parser to allocate hundreds of megabytes, leading to denial-of-service (DoS) through memory exhaustion.
5.3 (Medium)
Vendor Fix
Red Hat Hardened Images RPM Release
https://access.redhat.com/errata/RHSA-2026:5396
Workaround
To mitigate the issue, limit XML input size and complexity before parsing, and avoid accepting compressed or deeply nested XML. Use OS-level resource controls (like ulimit or setrlimit()) to cap memory usage, or run the parser in a sandboxed or isolated process with strict memory and CPU limits. This helps prevent denial-of-service by containing excessive resource consumption.
References
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"discovery_date": "2025-09-15T03:00:59.775098+00:00",
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"text": "A memory amplification vulnerability in libexpat allows attackers to trigger excessive dynamic memory allocations by submitting specially crafted XML input. A small input (~250 KiB) can cause the parser to allocate hundreds of megabytes, leading to denial-of-service (DoS) through memory exhaustion.",
"title": "Vulnerability description"
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"baseScore": 5.3,
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"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
"version": "3.1"
},
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}
],
"title": "firefox: thunderbird: expat: libexpat in Expat allows attackers to trigger large dynamic memory allocations via a small document that is submitted for parsing"
}
]
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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