Answer in brief
CVE-2026-103636 records a Unknown severity vulnerability in Apache DataSketches: datasketches-cpp: Out-of-bounds read in VarOpt union deserialization allows denial of service via a truncated sketch. The current sources do not mark it as known exploited. The current feed maps Apache Software Foundation/apache/datasketches-cpp (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Apache Software Foundation/apache/datasketches-cpp (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Apache Software Foundation/apache/datasketches-cppgeneric | >=2.0.0-incubating <=5.2.0 | Not reported |
Published upstream
Oct 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Oct 10, 2026
Out-of-bounds read in the VarOpt union deserialization of Apache DataSketches C++ (repo: datasketches-cpp). var_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. This 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. Users are recommended to upgrade to version 5.3.0, which fixes this issue.
Quoted source text, attributed separately from HOL analysis.