Elasticsearch Highlighting OOM DoS via Counting Bug
CVE-2026-72639 Published on August 13, 2026
Memory Allocation with Excessive Size Value in Elasticsearch Highlighting Leading to Denial of Service
Elasticsearch does not enforce an upper bound on a user-supplied count accepted by a search highlighting option, and the allocation derived from that count is not accounted against any circuit breaker. An authenticated user holding only read privileges on a single searchable index can submit one small search request that causes the node to reserve an excessively large internal data structure. The allocation occurs before the existing highlighting safety limits are evaluated, so memory exhaustion raises a fatal error that terminates the Elasticsearch node process. This results in a denial of service for the affected node and degrades cluster routing and health. The defect is not volumetric and does not depend on the size of the indexed data, so a single request is sufficient.
Vulnerability Analysis
CVE-2026-72639 can be exploited with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Type
What is a Stack Exhaustion Vulnerability?
The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.
CVE-2026-72639 has been classified to as a Stack Exhaustion vulnerability or weakness.
Products Associated with CVE-2026-72639
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Affected Versions
Elasticsearch:- Version 8.19.0, <= 8.19.19 is affected.
- Version 9.3.0, <= 9.5.0 is affected.