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Vulnerabilities

Vulnerability · CVE-2026-82397

Tornado: Urlencoded body parsing omits max_num_fields, so one request can stall the event loop

Published Aug 31, 2026 · catalog updated Sep 2, 2026 · Tornado: Urlencoded body parsing

Last checked Oct 31, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-82397. EPSS is 0.35%. Act only if a listed version of Tornado: Urlencoded body parsing is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Tornado: Urlencoded body parsing).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.35%
Remediation
Advisory link
Affected products
vendor tornadoweb tornado

Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.8, Tornado parses application/x-www-form-urlencoded request bodies with urllib.parse.parse_qs in tornado/escape.py without passing max_num_fields. RequestHandler._execute in tornado/web.py parses the body before handler dispatch through HTTPServerRequest._parse_body and parse_body_arguments in tornado/httputil.py, so an unauthenticated request body containing millions of separator-delimited fields can synchronously stall the single-threaded event loop and delay every connection. The body is bounded only by max_buffer_size, which defaults to 104857600 bytes. This issue is fixed in version 6.5.8.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor tornadoweb tornadoversion unspecified

How to fix CVE-2026-82397

  • No stored fix

    No vendor fix text is stored. Use the linked advisory before you change production.

  • Version check

    No version range is stored, so an installed version cannot be checked on this page.

  • Advisory

    Open the bsi record and follow its fix.

  • Official advisories

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-82397. EPSS is 0.35%. Act only if a listed version of Tornado: Urlencoded body parsing is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-1284; CWE-400: Uncontrolled Resource Consumption. EPSS 0.35%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Sep 2, 2026 · CVE.org

    Updated

    Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.8, Tornado parses application/x-www-form-urlencoded request bodies with urllib.parse.parse_qs in tornado/escape.py without passing max_num_fields. RequestHandler._execute in tornado/web.py parses the body before handler dispatch through HTTPServerRequest._parse_body and parse_body_arguments in tornado/httputil.py,

  2. Oct 30, 2026 · BSI CERT-Bund

    Detected

    CVE-2026-82397 is listed by Red Hat Enterprise Linux (python-tornado, resteasy-core, bubblewrap, pgvector): Mehrere Schwachstellen.

Sources

  • BSI CERT-BundGovernment advisoryCVE-2026-82397

    Red Hat Enterprise Linux (python-tornado, resteasy-core, bubblewrap, pgvector): Mehrere Schwachstellen

    wid.cert-bund.de
  • CVE.orgVulnerability recordCVE-2026-82397

    Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.8, Tornado parses application/x-www-form-urlencoded request bodies with urllib.parse.parse_qs in tornado/escape.py without passing max_num_fields. RequestHandler._execute in tornado/web.py parses

    cve.org

References

Freshness

Last verified in this catalog Oct 31, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • CVE.orgOct 31, 2026
  • BSI CERT-BundOct 31, 2026