CVE-2026-121564 Details
Description
Incomplete Comparison with Missing Factors (CWE-1023) in merge_chats() (whatstk/utils/chat_merge.py), reached from BaseChat.merge(), in whatstk from 0.3.0 before 0.9.0 allows a party that supplies the chat exports to cause messages to be absent from the merged output with no indication that anything was removed, because the merge keeps whole the chat whose first message is oldest and appends from the other only the messages that are strictly newer than the last message of the first. Every message of the second chat that falls inside the date range already covered by the first is therefore discarded. The two chats are compared on their date ranges and not on the identity of the individual messages, so a message held by only one of the two exports is dropped whenever its date falls inside the range of the other, and both branches of _merge_two_chats() behave this way. The merged result is returned without a warning and without a count of what was removed. This results in a merged chat that omits messages the inputs contain, in a library whose documented uses include forensic review and the generation of training data.
A vulnerability exists in the whatstk library, specifically in the chat merging function, versions 0.3.0 prior to 0.9.0. This vulnerability allows messages to be silently omitted when merging chat exports, with no indication of the missing content. The issue arises because the merging process prioritizes the chat with the oldest message and only adds messages from the second chat that are strictly newer. As a result, any message from the second chat that falls within the date range of the first chat is discarded, regardless of whether the first chat contains that message. This flaw is particularly concerning given whatstk's documented use cases, which include forensic analysis and training data generation, where such data loss could have significant consequences.
Users can upgrade to whatstk version 0.9.0 or later, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Nov 3, 2026CISA-ADP
Assessed Nov 3, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/lucasrodes/whatstk/commit/01d66d8 | Secur0 | Source CodeVendor |
| https://github.com/lucasrodes/whatstk/pull/185 | Secur0 | Issue TrackingVendor |
| https://github.com/lucasrodes/whatstk/releases/tag/v0.9.0 | Secur0 | Release NotesVendor |
| https://secur0.com/en/cna/cve-list/cve-2026-121564-whatstk-merge-message-loss | Secur0 | AdvisoryRemedy |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-1023 | Incomplete Comparison with Missing Factors | Secur0 |
Affected Products
| Product | Versions |
|---|---|
| whatstk | >= 0.3.0, < 0.9.0 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Nov 3, 2026 | CVE Modified | CISA-ADP |
| Nov 3, 2026 | New CVE Received | Secur0 |