CVE-2026-103501 Apache Software Foundation CVE debrief

Who should care

Defenders of applications using Apache DataSketches C++ versions from 1.0.0-incubating before 5.3.0, especially those deserializing HLL sketches from untrusted sources, should assess exposure and prioritize upgrading to version 5.3.0.

Why it matters

CVE-2026-103501 is a heap buffer overflow vulnerability in Apache DataSketches C++'s HLL sketch deserialization. Defenders of affected applications should prioritize upgrading to version 5.3.0 and restrict deserialization to trusted sources to prevent potential heap memory corruption and further exploitation.

• Potential heap memory corruption and crash
• Possible enabling of further exploitation
• Need to verify affected versions and upgrade to 5.3.0
• Importance of restricting deserialization to trusted sources

Technical summary

The vulnerability occurs in the HLL sketch deserialization of Apache DataSketches C++. When deserializing a sketch in LIST mode, the coupon count is read from the input and used as the number of entries to copy into a fixed buffer without checking it against the buffer's capacity. A crafted sketch could cause a write of up to 988 bytes past the end of this internal heap buffer, corrupting heap memory and potentially enabling further exploitation.

Defensive priority

Upgrade to version 5.3.0 and restrict deserialization of HLL sketches to trusted sources.

Recommended defensive actions

• Upgrade to Apache DataSketches C++ version 5.3.0
• Restrict deserialization of HLL sketches to trusted sources
• Review and update affected applications
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, affected versions, and recommended upgrade path. Apache DataSketches C++ versions from 1.0.0-incubating before 5.3.0 are affected. Only applications that deserialize HLL sketches from untrusted sources are impacted. Defenders should verify affected versions, assess exposure, and prioritize upgrading to version 5.3.0. Evidence is limited to public CVE and NVD records, with no additional internal or proprietary information available.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.