Sourced from The GitHub Security Advisory Database.

Catastrophic backtracking in URL authority parser when passed URL containing many @ characters

Impact

When provided with a URL containing many @ characters in the authority component the authority regular expression exhibits catastrophic backtracking causing a denial of service if a URL were passed as a parameter or redirected to via an HTTP redirect.

Patches

The issue has been fixed in urllib3 v1.26.5.

References

• CVE-2021-33503
• urllib3 v1.26.5

For more information

If you have any questions or comments about this advisory:

• Ask in our community Discord
• Email [email protected]

Affected versions: < 1.26.5

Sourced from urllib3's releases.

1.26.5

:warning: IMPORTANT: urllib3 v2.0 will drop support for Python 2: Read more in the v2.0 Roadmap

• Fixed deprecation warnings emitted in Python 3.10.
• Updated vendored six library to 1.16.0.
• Improved performance of URL parser when splitting the authority component.

If you or your organization rely on urllib3 consider supporting us via GitHub Sponsors

1.26.4

:warning: IMPORTANT: urllib3 v2.0 will drop support for Python 2: Read more in the v2.0 Roadmap

• Changed behavior of the default SSLContext when connecting to HTTPS proxy during HTTPS requests. The default SSLContext now sets check_hostname=True.

If you or your organization rely on urllib3 consider supporting us via GitHub Sponsors

1.26.3

:warning: IMPORTANT: urllib3 v2.0 will drop support for Python 2: Read more in the v2.0 Roadmap

• Fixed bytes and string comparison issue with headers (Pull #2141)

• Changed ProxySchemeUnknown error message to be more actionable if the user supplies a proxy URL without a scheme (Pull #2107)

If you or your organization rely on urllib3 consider supporting us via GitHub Sponsors

1.26.2

:warning: IMPORTANT: urllib3 v2.0 will drop support for Python 2: Read more in the v2.0 Roadmap

• Fixed an issue where wrap_socket and CERT_REQUIRED wouldn't be imported properly on Python 2.7.8 and earlier (Pull #2052)

1.26.1

:warning: IMPORTANT: urllib3 v2.0 will drop support for Python 2: Read more in the v2.0 Roadmap

• Fixed an issue where two User-Agent headers would be sent if a User-Agent header key is passed as bytes (Pull #2047)

1.26.0

:warning: IMPORTANT: urllib3 v2.0 will drop support for Python 2: Read more in the v2.0 Roadmap

• Added support for HTTPS proxies contacting HTTPS servers (Pull #1923, Pull #1806)

• Deprecated negotiating TLSv1 and TLSv1.1 by default. Users that still wish to use TLS earlier than 1.2 without a deprecation warning should opt-in explicitly by setting ssl_version=ssl.PROTOCOL_TLSv1_1 (Pull #2002) Starting in urllib3 v2.0: Connections that receive a DeprecationWarning will fail

• Deprecated Retry options Retry.DEFAULT_METHOD_WHITELIST, Retry.DEFAULT_REDIRECT_HEADERS_BLACKLIST and Retry(method_whitelist=...) in favor of Retry.DEFAULT_ALLOWED_METHODS, Retry.DEFAULT_REMOVE_HEADERS_ON_REDIRECT, and Retry(allowed_methods=...) (Pull #2000) Starting in urllib3 v2.0: Deprecated options will be removed

... (truncated)

Sourced from urllib3's changelog.

1.26.5 (2021-05-26)

• Fixed deprecation warnings emitted in Python 3.10.
• Updated vendored six library to 1.16.0.
• Improved performance of URL parser when splitting the authority component.

1.26.4 (2021-03-15)

• Changed behavior of the default SSLContext when connecting to HTTPS proxy during HTTPS requests. The default SSLContext now sets check_hostname=True.

1.26.3 (2021-01-26)

• Fixed bytes and string comparison issue with headers (Pull #2141)
• Changed ProxySchemeUnknown error message to be more actionable if the user supplies a proxy URL without a scheme. (Pull #2107)

1.26.2 (2020-11-12)

• Fixed an issue where wrap_socket and CERT_REQUIRED wouldn't be imported properly on Python 2.7.8 and earlier (Pull #2052)

1.26.1 (2020-11-11)

• Fixed an issue where two User-Agent headers would be sent if a User-Agent header key is passed as bytes (Pull #2047)

1.26.0 (2020-11-10)

• NOTE: urllib3 v2.0 will drop support for Python 2. Read more in the v2.0 Roadmap.
• Added support for HTTPS proxies contacting HTTPS servers (Pull #1923, Pull #1806)
• Deprecated negotiating TLSv1 and TLSv1.1 by default. Users that still wish to use TLS earlier than 1.2 without a deprecation warning should opt-in explicitly by setting ssl_version=ssl.PROTOCOL_TLSv1_1 (Pull #2002) Starting in urllib3 v2.0: Connections that receive a DeprecationWarning will fail
• Deprecated Retry options Retry.DEFAULT_METHOD_WHITELIST, Retry.DEFAULT_REDIRECT_HEADERS_BLACKLIST and Retry(method_whitelist=...) in favor of Retry.DEFAULT_ALLOWED_METHODS, Retry.DEFAULT_REMOVE_HEADERS_ON_REDIRECT, and Retry(allowed_methods=...) (Pull #2000) Starting in urllib3 v2.0: Deprecated options will be removed
• Added default User-Agent header to every request (Pull #1750)
• Added urllib3.util.SKIP_HEADER for skipping User-Agent, Accept-Encoding, and Host headers from being automatically emitted with requests (Pull #2018)
• Collapse transfer-encoding: chunked request data and framing into the same socket.send() call (Pull #1906)
• Send http/1.1 ALPN identifier with every TLS handshake by default (Pull #1894)
• Properly terminate SecureTransport connections when CA verification fails (Pull #1977)
• Don't emit an SNIMissingWarning when passing server_hostname=None to SecureTransport (Pull #1903)
• Disabled requesting TLSv1.2 session tickets as they weren't being used by urllib3 (Pull #1970)
• Suppress BrokenPipeError when writing request body after the server has closed the socket (Pull #1524)
• Wrap ssl.SSLError that can be raised from reading a socket (e.g. "bad MAC") into an urllib3.exceptions.SSLError (Pull #1939)

• d161647 Release 1.26.5
• 2d4a3fe Improve performance of sub-authority splitting in URL
• 2698537 Update vendored six to 1.16.0
• 07bed79 Fix deprecation warnings for Python 3.10 ssl module
• d725a9b Add Python 3.10 to GitHub Actions
• 339ad34 Use pytest==6.2.4 on Python 3.10+
• f271c9c Apply latest Black formatting
• 1884878 [1.26] Properly proxy EOF on the SSLTransport test suite
• a891304 Release 1.26.4
• 8d65ea1 Merge pull request from GHSA-5phf-pp7p-vc2r
• Additional commits viewable in compare view

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