# CVE-2026-100302: Apache ZooKeeper: Denial of service through unbounded memory allocation in multiRead request handling

Status: published. Published: 2026-11-04. Updated: 2026-11-04.

Allocation of Resources Without Limits or Throttling in the multiRead request handler of Apache ZooKeeper allows a remote attacker to crash the server (denial of service) with a single small request.

The multiRead handler places no limit on the number of bundled read operations or on the cumulative size of the response it builds in memory. Because each operation's result is fully materialized and retained before serialization, a request that is small on the wire — within the jute.maxbuffer limit — but that references a large znode many times can force the server to allocate far more heap than the request size implies, exhausting the JVM heap and terminating the server with an OutOfMemoryError. Neither jute.maxbuffer nor largeRequestMaxBytes prevents this, as both bound only the inbound request, not the response.

This issue affects Apache ZooKeeper from 3.7.0 through 3.9.6. Users are recommended to upgrade to version 3.9.7, which enforces configurable limits on the multiRead operation count and cumulative response size.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Apache Software Foundation / Apache ZooKeeper (org.apache.zookeeper:zookeeper): ≥ 3.9.0; ≤ 3.9.6 (affected, maven); ≥ 3.8.0; ≤ 3.8.7 (affected, maven). Source: CNA: apache

## Severity and prioritization

- CVSS 4.0: 7.1 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: apache

- CVSS 4.0: 7.1 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: security@apache.org

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-770

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://lists.apache.org/thread.html/gj2vxwx8myq31js6tvb7bgls4nnxohj7 (CNA: apache; vendor-advisory)

- http://www.openwall.com/lists/oss-security/2026/11/03/12 (ADP: CVE)

- https://lists.apache.org/thread.html/gj2vxwx8myq31js6tvb7bgls4nnxohj7 (security@apache.org)

- http://www.openwall.com/lists/oss-security/2026/11/03/12 (af854a3a-2127-422b-91ae-364da2661108)

## Provenance

- CNA: apache: https://www.cve.org/CVERecord?id=CVE-2026-100302; retrieved 2026-11-04; source updated 2026-11-04

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-100302; retrieved 2026-11-04; source updated 2026-11-04

Revision: 28b53b62a281ed504cc30979074ba2cad43954fca2531025f8ffd222f73b4ea4

Canonical: https://y2.dev/cve/CVE-2026-100302

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.