Ecosyste.ms: Advisories

Security Advisories: GSA_kwCzR0hTQS1xcHB2LWo3NmgtMnJweM4AA1Sz

Tornado vulnerable to HTTP request smuggling via improper parsing of `Content-Length` fields and chunk lengths

Summary

Tornado interprets -, +, and _ in chunk length and Content-Length values, which are not allowed by the HTTP RFCs. This can result in request smuggling when Tornado is deployed behind certain proxies that interpret those non-standard characters differently. This is known to apply to older versions of haproxy, although the current release is not affected.

Details

Tornado uses the int constructor to parse the values of Content-Length headers and chunk lengths in the following locations:

tornado/http1connection.py:445

            self._expected_content_remaining = int(headers["Content-Length"])

tornado/http1connection.py:621

                content_length = int(headers["Content-Length"])  # type: Optional[int]

tornado/http1connection.py:671

            chunk_len = int(chunk_len_str.strip(), 16)

Because int("0_0") == int("+0") == int("-0") == int("0"), using the int constructor to parse and validate strings that should contain only ASCII digits is not a good strategy.

Permalink: https://github.com/advisories/GHSA-qppv-j76h-2rpx
JSON: https://advisories.ecosyste.ms/api/v1/advisories/GSA_kwCzR0hTQS1xcHB2LWo3NmgtMnJweM4AA1Sz
Source: GitHub Advisory Database
Origin: Unspecified
Severity: Moderate
Classification: General
Published: 9 months ago
Updated: 8 months ago

Identifiers: GHSA-qppv-j76h-2rpx
References:

• https://github.com/tornadoweb/tornado/security/advisories/GHSA-qppv-j76h-2rpx
• https://github.com/tornadoweb/tornado/commit/b7a5dd29bb02950303ae96055082c12a1ea0a4fe
• https://github.com/advisories/GHSA-qppv-j76h-2rpx

Repository: https://github.com/tornadoweb/tornado
Blast Radius: 0.0

Affected Packages