CVE-2026-121691

MEDIUMPre-NVD 6.76.7
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This medium-severity CVE scores 6.7 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1% (3rd percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source

Also known asEUVD-2026-121394 (ENISA EUVD) · GHSA-q683-6fhr-jvg2 (GitHub Security Advisories)Source: ENISA EUVD

6.7EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.1%CVSS: 6.7Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Fixed versions, as the CVE record's CNA (Secur0) states them: "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."

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.

CVSS
6.7
EG Score
6.7MEDIUMmedium confidence
EG Risk
30
EG Risk 30/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity67% × 45%
Impact severity (EG Severity): CVSS 6.7 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.1% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's BOD 26-04 default: no one has published Automatable for this CVE, and CISA treats it as “no” for a CVE not in KEV.
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact partial (CVSS v4.0 confidentiality and integrity impact neither High). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.1%
EPSS %ILE
3rd
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (6.7): severity, escalated by confirmed exploitation. This CVE's 6.7 is its impact severity (EG Severity), not escalated.

EG Severity
6.7 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source
EG Likelihood
0.1% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-12). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact partial (CVSS v4.0 confidentiality and integrity impact neither High). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact partial (CVSS v4.0 confidentiality and integrity impact neither High). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

November 10, 2026

Last Modified

November 12, 2026

Advisory Details (4)

Auto-updated Nov 12, 2026
Patch available. Sources: github_commit, github_pr, github_release.
Web page

CVE-2026-121691 · Unbounded decompression in the… | Secur0

https://secur0.com/en/cna/cve-list/cve-2026-121691-whatstk-zip-decompression-bomb
GitHub release Patch Available

v0.9.0

Patch available: lucasrodes/whatstk v0.9.0

https://github.com/lucasrodes/whatstk/releases/tag/v0.9.0
GitHub pull request Patch Available

Bound how much chat text is read from a source (report #1800)

Patch available: lucasrodes/whatstk v0.9.1 (PR #182 merged 2026-10-23)

https://github.com/lucasrodes/whatstk/pull/182
GitHub commit Patch Available

commit 01d66d8 (lucasrodes/whatstk)

Patch available: lucasrodes/whatstk v0.9.0 (contains commit 01d66d8)

https://github.com/lucasrodes/whatstk/commit/01d66d8

Vendor Advisories for CVE-2026-121691(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 7× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed its CVE.org record (CNA or CISA ADP). An arrow marks a change the record states ("CVSS → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

  1. 2026-11-13 16:50 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  2. 2026-11-12 22:30 UTCEchelonGraph re-scored
  3. 2026-11-12 22:30 UTCGHSA enrichmentGHSA-q683-6fhr-jvg2 · GitHub severity MODERATE
  4. 2026-11-11 16:38 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  5. 2026-11-11 07:26 UTCGHSA enrichmentGHSA-q683-6fhr-jvg2 · GitHub severity MODERATE
  6. 2026-11-10 18:37 UTCEchelonGraph re-scored
  7. 2026-11-10 18:37 UTCGHSA enrichmentGHSA-q683-6fhr-jvg2 · GitHub severity MODERATE
  8. 2026-11-10 18:00 UTCENISA EUVD ID recordedEUVD-2026-121394 · Source: ENISA EUVD
  9. 2026-11-10 17:35 UTCEchelonGraph re-scoredFirst assessed: 6.7 MEDIUM
  10. 2026-11-10 17:34 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-121691?
CVE-2026-121691 is a medium-severity vulnerability; its CVE record was published on November 10, 2026. 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()…
When was the CVE record for CVE-2026-121691 published?
The CVE record for CVE-2026-121691 was published on November 10, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of November 12, 2026; the record at its source may have been updated since.
Is CVE-2026-121691 actively exploited?
CVE-2026-121691 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.1% probability of exploitation in the next 30 days (3rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-121691?
CVE-2026-121691 has a CVSS base score of 6.7 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-121691?
A fix for CVE-2026-121691 is available: update to the fixed version the vendor names in its advisory. Fixed versions, as the CVE record's CNA (Secur0) states them: "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." The vendor advisories EchelonGraph has for CVE-2026-121691 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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