---
id: "CVE-2026-121691"
page: "https://infrastack.ai/live/CVE-2026-121691"
kind: "vulnerability"
aliases: ["CVE-2026-121691"]
title: "whatstk: crafted ZIP chat export exhausts memory and disk"
severity: "medium"
cvss: 6.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["package", "python", "whatstk"]
not_affected_if: ["no-zip-input", "trusted-input-only"]
published_at: "2026-11-10T18:17:20+00:00"
first_seen_at: "2026-11-10T18:22:55+00:00"
updated_at: "2026-11-10T18:24:50+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121691", "first_seen_at": "2026-11-10T18:22:55+00:00"}]
exploit_sources: []
---

# whatstk: crafted ZIP chat export exhausts memory and disk

Link for people: https://infrastack.ai/live/CVE-2026-121691 (this .md is for agents)

whatstk's ZIP loader extracts a chat export without size or compression-ratio limits, so a small archive can fill memory and disk. An attacker who supplies a crafted WhatsApp export can crash or stall the process that parses it.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed version with `pip show whatstk` and see whether it is below `0.9.0`.
- Look for code that calls `WhatsAppChat.from_source()` or `df_from_whatsapp()` on uploaded or user-supplied ZIP files.

## Fix

- `whatstk` `0.9.0` (the fix for affected versions from `0.7.0` before `0.9.0`, per the linked patch and release notes).

## Timeline

- 2026-11-10T18:22:55+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121691

## Documents

- [fix] Patch: github.com https://github.com/lucasrodes/whatstk/commit/01d66d8
- [fix] Release notes: github.com https://github.com/lucasrodes/whatstk/releases/tag/v0.9.0

## From the sources

Improper Handling of Highly Compressed Data (CWE-409) in the ZIP loader of whatstk from 0.7.0 before 0.9.0 allows a party that supplies a chat export to exhaust the memory and the disk of the process that parses it, because _str_from_file() (whatstk/whatsapp/parser.py) calls zip_ref.extractall() with no bound on the size of the members and no check of the compression ratio, then reads the extracted file in full with f.read(). The only guard on the archive counts the extracted files and raises when there is not exactly one, but it runs after extractall() has already written them, so it does not prevent the cost. _clean_text() then passes the whole text through unicodedata.normalize("NFKD", text), which holds a second copy, and the parse builds a list of regular expression matches and a DataFrame over it, so peak memory is a multiple of the decompressed text rather than of the archive. A ZIP is a documented input of WhatsAppChat.from_source() and df_from_whatsapp(), and is the form in which WhatsApp exports a chat on iOS, so the attacker supplies the whole file. This results in a small upload costing hundreds of megabytes of memory and of disk, and in the process being killed where that exceeds what is available.

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