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CVE-2026-91990VulnerabilityPublished Updated

nvchecker · tornado: multipart split() creates huge temp list before max_parts check -> memory amplification DoS (httputil.py:34)

Affects nvcheckerSource GCVE Database

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Authoritative record:CVE-2026-91990· High 8.7

Not known to be exploited · CVSS 8.7 High : upgrade to 2.22 soon.

Data as of 30 Oct 2026, 07:30 UTC

CVSS 4.0 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 2.22
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 15 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade nvchecker to 2.22.

Affected software

ProductAffectedFixed in
Homebrewnvcheckerpkg:brew/nvcheckerOther threatsAffected
  • >=2.7 <2.22
Fixed in
  • 2.22

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

## Description ### Summary `parse_multipart_form_data` (httputil.py:34) calls `data.split(b"--"+boundary+b"\r\n")` **before** the `max_parts` check (:35). A 600KB body with 100k parts creates a 100k-element transient list first, then rejects transient memory amplification (each split element is a copy). Pre-auth HTTP DoS. ### Root cause ```python parts = data[:final_boundary_index].split(b"--" + boundary + b"\r\n") # :34 huge list first if len(parts) > config.max_parts: # :35 check after raise HTTPInputError("multipart/form-data has too many parts") ``` ### PoC gist: https://gist.github.com/afldl/649861f25d39b53b7edbe0298e171617 `poc.py` + `output.txt` (100k parts from 600KB transient list). ### Fix Count separators without materializing the list (e.g. `data.count(b"--"+boundary)` first). ### Credit Reported by afldl, 2026-07.

References

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