{"cve":"CVE-2026-103636","nvd":{"published":"2026-10-10T11:17:36.077","modified":"2026-10-16T16:16:53.970","status":"Undergoing Analysis","description":"Out-of-bounds read in the VarOpt union deserialization of Apache DataSketches C++ (repo: datasketches-cpp).\n\nvar_opt_union::deserialize() read the 32-byte preamble of a non-empty union after checking that only 8 bytes were available, so a truncated serialized union could cause a read of up to 24 bytes past the end of the input. For such inputs, the size remaining for the embedded sketch was also computed by an unsigned subtraction that could wrap around, so the embedded sketch's own size checks no longer limited reads to the input. The bytes read can become part of the deserialized union's state. This can cause a crash (denial of service) and could expose adjacent memory contents.\n\nThis issue affects Apache DataSketches C++: from 2.0.0-incubating before 5.3.0. Only applications that deserialize VarOpt unions from untrusted sources are affected.\n\nUsers are recommended to upgrade to version 5.3.0, which fixes this issue.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-125","CWE-191"],"references":["https://github.com/apache/datasketches-cpp/releases/tag/5.3.0","https://lists.apache.org/thread/znn94s463w7wy125khcywxsp82y2qkq5","http://www.openwall.com/lists/oss-security/2026/10/10/6"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:58:01.639778232+00:00"},"epss":{"cve":"CVE-2026-103636","score":0.0038,"percentile":0.31671,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}