Unbounded decompression in the whatstk ZIP loader exhausts memory and disk
Summary
| CVE | CVE-2026-121691 |
|---|---|
| State | PUBLISHED |
| Assigner | Secur0 |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-11-10 18:17:20 UTC |
| Updated | 2026-11-10 18:17:20 UTC |
| Description | 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. |
Risk And Classification
Primary CVSS: v4.0 6.7 MEDIUM from 4daa8cea-433a-44bd-9456-53b127fc289a
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Problem Types: CWE-409 | CWE-409 CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | 4daa8cea-433a-44bd-9456-53b127fc289a | Secondary | 6.7 | MEDIUM | CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/C... |
| 4.0 | CNA | CVSS | 6.7 | MEDIUM | CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N |
CVSS v4.0 Breakdown
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Lucasrodes | Whatstk | affected 0.7.0 0.9.0 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/lucasrodes/whatstk/pull/182 | 4daa8cea-433a-44bd-9456-53b127fc289a | github.com | |
| github.com/lucasrodes/whatstk/releases/tag/v0.9.0 | 4daa8cea-433a-44bd-9456-53b127fc289a | github.com | |
| github.com/lucasrodes/whatstk/commit/01d66d8 | 4daa8cea-433a-44bd-9456-53b127fc289a | github.com | |
| secur0.com/en/cna/cve-list/cve-2026-121691-whatstk-zip-decompression-bomb | 4daa8cea-433a-44bd-9456-53b127fc289a | secur0.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Jorge Rey Cotallo (reddev) (en)
CNA: Xoán M. Otero Jorge (en)
CNA: Darío Rivas (en)
CNA: Secur0 CNA (en)
CNA: Lucas Rodés-Guirao (en)
Additional Advisory Data
Solutions
CNA: Upgrade to whatstk 0.9.0 or later, which rejects a source larger than 50 MB by default and accepts a max_size argument to lower that bound.