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VulnerabilityPublished Updated

CVE-2026-31958: Nvchecker · Tornado is vulnerable to DoS due to too many multipart parts

Affects nvcheckerSource GCVE Database

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Authoritative record:CVE-2026-31958· High 8.7

Not known to be exploited · CVSS 8.7 High : upgrade to 2.20_1 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 2.20_1
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 11 Mar 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 2.20_1.

Affected software

ProductAffectedFixed in
Homebrewnvcheckerpkg:brew/nvcheckerOther threatsAffected
  • >=2.7 <2.20_1
Fixed in
  • 2.20_1

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

Description

In versions of Tornado prior to 6.5.5, the only limit on the number of parts in `multipart/form-data` is the `max_body_size` setting (default 100MB). Since parsing occurs synchronously on the main thread, this creates the possibility of denial-of-service due to the cost of parsing very large multipart bodies with many parts. Tornado 6.5.5 introduces new limits on the size and complexity of multipart bodies, including a default limit of 100 parts per request. These limits are configurable if needed; see `tornado.httputil.ParseMultipartConfig`. It is also now possible to disable `multipart/form-data` parsing entirely if it is not required for the application.

References

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