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GHSA-v6wp-4m6f-gcjg CVE-2021-21330 PYSEC-2021-76

`aiohttp` Open Redirect vulnerability (`normalize_path_middleware` middleware)

Low PyPI
Severity
0.0 / 10
Low · CVSS 4.0
Exploit chance (EPSS)
1.91%
Chance of exploitation in the next 30 days. Higher than 79.72% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
CWE-601 URL Redirection to Untrusted Site ('Open Redirect')
Fix
3.7.4
Upgrade aiohttp to this version or later

Description

Impact

Open redirect vulnerability — a maliciously crafted link to an aiohttp-based web-server could redirect the browser to a different website.

It is caused by a bug in the aiohttp.web_middlewares.normalize_path_middleware middleware.

Patches

This security problem has been fixed in v3.7.4. Upgrade your dependency as follows: pip install aiohttp >= 3.7.4

Workarounds

If upgrading is not an option for you, a workaround can be to avoid using aiohttp.web_middlewares.normalize_path_middleware in your applications.

References

For more information

If you have any questions or comments about this advisory:

Credit: Jelmer Vernooij and Beast Glatisant.

Affected versions

PyPI

PackageVulnerableFixed in
aiohttp
< 3.7.4
3.7.4
aiohttp
< 3.7.4
3.7.4

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

aiohttp PyPI → 3.7.4

pip
pip install --upgrade "aiohttp>=3.7.4"
poetry
poetry add "aiohttp>=3.7.4"
uv
uv add "aiohttp>=3.7.4"

Severity breakdown

CVSS 4.0 0.0

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Attack vector
Network
Attack complexity
Low
Attack requirements
Present
Privileges required
None
User interaction
Passive
Confidentiality (vulnerable system)
None
Integrity (vulnerable system)
Low
Availability (vulnerable system)
None
Confidentiality (subsequent systems)
None
Integrity (subsequent systems)
None
Availability (subsequent systems)
None

CVSS 3.1 3.1

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

Weakness

CWE-601: URL Redirection to Untrusted Site ('Open Redirect')

The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.

How to prevent it
  • Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. Use a list of approved URLs or domains to be used for redirection.
  • Architecture and Design: Use an intermediate disclaimer page that provides the user with a clear warning that they are leaving the current site. Implement a long timeout before the redirect occurs, or force the user to click on the link. Be careful to avoid XSS problems (CWE-79) when generating the disclaimer page.
  • Architecture and Design: When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs. For example, ID 1 could map to "/login.asp" and ID 2 could map to "http://www.example.com/". Features such as the ESAPI AccessReferenceMap [REF-45] provide this capability.
  • Architecture and Design: Ensure that no externally-supplied requests are honored by requiring that all redirect requests include a unique nonce generated by the application [REF-483]. Be sure that the nonce is not predictable (CWE-330).
  • Architecture and Design, Implementation: Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls. Many open redirect problems occur because the programmer assumed that certain inputs could not be modified, such as cookies and hidden form fields.
  • Operation: Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].

References

Advisories

Packages

Other links

Timeline

  1. Published
  2. Last updated by the source
  3. Latest EPSS score
AdvisorySeverityWhy it's related
GHSA-pqxq-w44r-73xw
AIOHTTP: Pure-Python parser request smuggling
Medium Also affects aiohttp
GHSA-gx76-c99x-2c96
AIOHTTP: Cookie from subdomain can remove Host-Only Scope from existing cookies
Low Also affects aiohttp
GHSA-f9xw-jh8m-3mwq
AIOHTTP: Absolute-form request targets can spoof Request.scheme
Medium Also affects aiohttp
GHSA-9xw5-w5jj-pvcg
AIOHTTP: File descriptor exhaustion in multipart requests
High Also affects aiohttp
GHSA-6cjc-53gc-5rqm
AIOHTTP: Connector pool exhaustion via Max-Age overflow
Medium Also affects aiohttp
GHSA-5wr8-gcqf-gqf3
aiohttp server lacks an initial request/header timeout
High Also affects aiohttp
GHSA-494j-54xm-rwp3
AIOHTTP: Secure attribute not enforced for shared cookie
Medium Also affects aiohttp
GHSA-2g87-pp6c-29x5
aiohttp: Multiple instances of excessive or unbounded memory/CPU use
High Also affects aiohttp
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