Update dependency tornado to v6.5.8 [SECURITY]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
tornado (source)	6.5.7 → 6.5.8

---

Tornado: Incomplete fix for CVE-2026-35536: cookie attribute injection re-opened via the legacy case-insensitive **kwargs path in set_cookie

GHSA-wwv5-g3v4-889x

More information

Details

Summary

The CVE-2026-35536 fix added a validation loop that rejects [\x00-\x20\x3b\x7f], but only for the
hardcoded lowercase keys name/domain/path/samesite. The still-live deprecated **kwargs path
writes attacker-supplied attribute values straight into the Morsel with no validation, and because
Morsel.__setitem__ is case-insensitive, a capitalized kwarg (Domain=, Path=, SameSite=, Max-Age=)
routes to the same reserved attribute while bypassing the loop — re-opening ;-delimited attribute injection.

self.set_cookie("sid", "abc", Domain="evil.com; Secure; SameSite=None")

#####  -> Set-Cookie: sid=abc; Domain=evil.com; Secure; SameSite=None; Path=/
##### Sanity (the canonical lowercase named arg IS blocked):
self.set_cookie("sid", "abc", domain="evil.com; Secure")   # -> http.cookies.CookieError

The patch's regression test (SetCookieForbiddenCharHandler) only exercises the four named params, never the
**kwargs path, so the gap is not regression-covered.

Affected code

• tornado/web.py → RequestHandler.set_cookie: the validation loop covers only the lowercase named args;
  the trailing if kwargs: loop does morsel[k] = v with no character validation.

Steps to reproduce

GET /upper (uses Domain= kwarg) emits Set-Cookie: c_upper=v; Domain=evil.com; Secure; SameSite=None; Path=/; GET /lower (uses lowercase
domain=) returns a CookieError.

Impact

Injection of independent cookie attributes (force/drop Secure/HttpOnly/SameSite, rebind Domain/Path)
— the same impact CVE-2026-35536 closed, via the sibling path the patch missed. Conditional on the app using
a capitalized/legacy keyword.

Suggested remediation

Apply the same [\x00-\x20\x3b\x7f] validation to every entry in the **kwargs loop (after normalizing the
key case), or remove the deprecated kwargs path; add a regression test for capitalized kwargs.

Credit

Reported as part of an incomplete-patch measurement study (responsible disclosure).

Severity

• CVSS Score: 2.3 / 10 (Low)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

References

• https://github.com/tornadoweb/tornado/security/advisories/GHSA-wwv5-g3v4-889x
• https://github.com/tornadoweb/tornado/pull/3704
• https://github.com/tornadoweb/tornado/pull/3706
• https://github.com/tornadoweb/tornado/commit/6ef836e43e1278530041376adb32504daa977b91
• https://github.com/tornadoweb/tornado/commit/da284767eae8e1f0484f123b8c3225f6465b09c7
• https://github.com/tornadoweb/tornado/releases/tag/v6.5.8
• https://github.com/advisories/GHSA-wwv5-g3v4-889x

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

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

GHSA-8423-8fgw-73vq

More information

Details

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

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.

Severity

• CVSS Score: 6.9 / 10 (Medium)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

References

• https://github.com/tornadoweb/tornado/security/advisories/GHSA-8423-8fgw-73vq
• https://github.com/tornadoweb/tornado/pull/3704
• https://github.com/tornadoweb/tornado/commit/de85b3f87446e323e881bbaa3d5a74f4b76e5f05
• https://gist.github.com/afldl/649861f25d39b53b7edbe0298e171617
• https://github.com/tornadoweb/tornado/releases/tag/v6.5.8
• https://github.com/advisories/GHSA-8423-8fgw-73vq

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

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

CVE-2026-82397 / GHSA-mpf4-983q-p7j4

More information

Details

Summary

Tornado parses application/x-www-form-urlencoded bodies with urllib.parse.parse_qs and does not pass max_num_fields. A body made almost entirely of separators produces tens of millions of fields, and the parse happens on the event loop before the handler runs, so a single request stalls the whole server.

Where it is

tornado/escape.py, at HEAD e530031405e2154654dedc4c84d5656b557ea310:

result = urllib.parse.parse_qs(
    qs, keep_blank_values, strict_parsing, encoding="latin1", errors="strict"
)

max_num_fields is the parameter CPython added for exactly this, and it is absent.

The path to it is entirely server-side and pre-dispatch. RequestHandler._execute parses the body at tornado/web.py:1821, which reaches HTTPServerRequest._parse_body at tornado/httputil.py:636, and the urlencoded branch of parse_body_arguments calls parse_qs_bytes at tornado/httputil.py:1030.

The size that reaches it is bounded only by the body cap, which defaults to the stream's max_buffer_size of 104857600 at tornado/iostream.py:239, applied as the request body default at tornado/http1connection.py:136-140. A 100 MB body of separators is around fifty million fields.

Impact

Denial of service against the whole process, not one request. Tornado is single-threaded and the parse is synchronous on the event loop, so every other connection waits. No authentication is needed if any route accepts a form post, which is the normal case.

Suggested fix

Pass a bound:

result = urllib.parse.parse_qs(
    qs, keep_blank_values, strict_parsing, encoding="latin1", errors="strict",
    max_num_fields=max_num_fields,
)

with a conservative default and a way for applications to raise it. CPython raises ValueError when the limit is exceeded, which maps cleanly onto a 400.

Lowering the default body cap for urlencoded specifically would help too, since 100 MB of form fields is not a shape any real client sends.

Why I do not think this is a duplicate

The published tornado advisories cover out-of-bounds access in the C extension, unbounded accumulation of decompressed chunks in AsyncHTTPClient, the Authorization header surviving cross-origin redirects, credential leakage on curl handle reuse, and cookie attribute validation. The decompression one is the nearest in spirit and is on the client side; this is the server parsing a request body. The call is unchanged at HEAD.

Severity

• CVSS Score: 7.5 / 10 (High)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

• https://github.com/tornadoweb/tornado/security/advisories/GHSA-mpf4-983q-p7j4
• https://nvd.nist.gov/vuln/detail/CVE-2026-82397
• https://github.com/tornadoweb/tornado/pull/3704
• https://github.com/tornadoweb/tornado/commit/8d6363ed7b69d5f0da806efe34d256627a2191de
• https://github.com/tornadoweb/tornado/releases/tag/v6.5.8
• https://github.com/advisories/GHSA-mpf4-983q-p7j4

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Release Notes

tornadoweb/tornado (tornado)

v6.5.8

Compare Source

---

Configuration

📅 Schedule: (UTC)

• Branch creation
  • At any time (no schedule defined)
• Automerge
  • At any time (no schedule defined)

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• If you want to rebase/retry this PR, check this box

---

This PR was generated by Mend Renovate. View the repository job log.

[coderabbitai]

Important

Review skipped

Bot user detected.

To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Organization UI

Review profile: QUIET

Plan: Advanced

Run ID: 50a134cb-9488-4db6-b8f0-e7bfdfeadabc

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[dkropachev]

Superseded by #1042, which bundles this tornado security update with all remaining documentation dependency alerts.

[renovate]

Renovate Ignore Notification

Because you closed this PR without merging, Renovate will ignore this update (>=6.5,<7.0). You will get a PR once a newer version is released. To ignore this dependency forever, add it to the ignoreDeps array of your Renovate config.

If you accidentally closed this PR, or if you changed your mind: rename this PR to get a fresh replacement PR.