Service interrupt via inverted getentropy check
Published Aug 20, 2026 · Updated Aug 20, 2026
Insufficient entropy in libexpat 2.8.2 and 2.8.3 before 2.8.4 allows remote attackers to cause a denial of service via crafted XML. In expat/lib/random_getentropy.c, writeRandomBytes_getentropy stores getentropy()'s 0-on-success return in a bool, inverting the success test so successful reads are treated as failures and the parser falls back from strong hash-salt entropy. Exposure is limited to builds that use the getentropy provider; applications that parse attacker-controlled XML can then suffer hash-flooding CPU exhaustion rather than code execution or data tampering.
Summary
What happened
Insufficient entropy in libexpat 2.8.2 and 2.8.3 before 2.8.4 allows remote attackers to cause a denial of service via crafted XML. In expat/lib/random_getentropy.c, writeRandomBytes_getentropy stores getentropy()'s 0-on-success return in a bool, inverting the success test so successful reads are treated as failures and the parser falls back from strong hash-salt entropy. Exposure is limited to builds that use the getentropy provider; applications that parse attacker-controlled XML can then suffer hash-flooding CPU exhaustion rather than code execution or data tampering.
The record
- CVE
- CVE-2026-76956
- Published
- Aug 20, 2026
- Updated
- Aug 20, 2026
- Vendor
- Expat Project
- Product
- libexpat
- Classifications
- CWE-394, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 20, 2026CVE publishedPublication date reported by the CVE source.
- Aug 20, 2026Record 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?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=2.8.2 <2.8.4
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
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
No public exploit references are available in this record.
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