Denial of service via miscalculated amplification ratio
Published Mar 10, 2024 · Updated Nov 4, 2025
Denial of service in libexpat through 2.6.1 allows remote attackers to hang applications via crafted external DTD input. In accountingGetCurrentAmplification, isolated external parsers record zero direct bytes, so the zero-denominator fallback reports an amplification ratio of 1.0 and bypasses the entity-expansion limit. Reachability requires an application to feed attacker-controlled DTD content directly to a parser created by XML_ExternalEntityParserCreate; successful expansion consumes processing resources until the application stalls.
Summary
What happened
Denial of service in libexpat through 2.6.1 allows remote attackers to hang applications via crafted external DTD input. In accountingGetCurrentAmplification, isolated external parsers record zero direct bytes, so the zero-denominator fallback reports an amplification ratio of 1.0 and bypasses the entity-expansion limit. Reachability requires an application to feed attacker-controlled DTD content directly to a parser created by XML_ExternalEntityParserCreate; successful expansion consumes processing resources until the application stalls.
The record
- CVE
- CVE-2024-28757
- Published
- Mar 10, 2024
- Updated
- Nov 4, 2025
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-776, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 10, 2024CVE publishedPublication date reported by the CVE source.
- Nov 4, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Isolated external-parser entity-expansion reproducerproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo