Mailman 3 - Security-announce

[CVE-2026-1703] Limited path traversal when installing wheel archives
by Seth Larson Feb. 2, 2026

Feb. 2, 2026

There is a LOW severity vulnerability affecting pip. When pip is installing and extracting a maliciously crafted wheel archive, files may be extracted outside the installation directory. The path traversal is limited to prefixes of the installation directory, thus isn't able to inject or overwrite executable files in typical situations. Please see the linked CVE ID for the latest information on affected versions: * https://www.cve.org/CVERecord?id=CVE-2026-1703 * https://github.com/pypa/pip/pull/13777

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[CVE-2026-1299] email BytesGenerator header injection due to unquoted newlines
by Seth Larson Jan. 23, 2026

Jan. 23, 2026

There is a MEDIUM severity vulnerability affecting CPython. The email module, specifically the "BytesGenerator" class, didn’t properly quote newlines for email headers when serializing an email message allowing for header injection when an email is serialized. This is only applicable if using "LiteralHeader" while writing headers that don't respect email folding rules, the new behavior will reject the incorrectly folded headers in "BytesGenerator". Please see the linked CVE ID for the latest information on affected versions: * https://www.cve.org/CVERecord?id=CVE-2026-1299 * https://github.com/python/cpython/pull/144126

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[CVE-2025-12781] base64.b64decode() always accepts "+/" characters, despite setting altchars
by Seth Larson Jan. 21, 2026

Jan. 21, 2026

There is a MEDIUM severity vulnerability affecting CPython. When passing data to the b64decode(), standard_b64decode(), and urlsafe_b64decode() functions in the "base64" module the characters "+/" will always be accepted, regardless of the value of "altchars" parameter, typically used to establish an "alternative base64 alphabet" such as the URL safe alphabet. This behavior matches what is recommended in earlier base64 RFCs, but newer RFCs now recommend either dropping characters outside the specified base64 alphabet or raising an error. The old behavior has the possibility of causing data integrity issues. This behavior can only be insecure if your application uses an alternate base64 alphabet (without "+/"). If your application does not use the "altchars" parameter or the urlsafe_b64decode() function, then your application does not use an alternative base64 alphabet. The attached patches DO NOT make the base64-decode behavior raise an error, as this would be a change in behavior and break existing programs. Instead, the patch deprecates the behavior which will be replaced with the newly recommended behavior in a future version of Python. Users are recommended to mitigate by verifying user-controlled inputs match the base64 alphabet they are expecting or verify that their application would not be affected if the b64decode() functions accepted "+" or "/" outside of altchars. Please see the linked CVE ID for the latest information on affected versions: * https://www.cve.org/CVERecord?id=CVE-2025-12781 * https://github.com/python/cpython/pull/141128

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[CVE-2026-0672] Header injection in http.cookies.Morsel
by Seth Larson Jan. 20, 2026

Jan. 20, 2026

There is a MEDIUM severity vulnerability affecting CPython. When using http.cookies.Morsel, user-controlled cookie values and parameters can allow injecting HTTP headers into messages. Patch rejects all control characters within cookie names, values, and parameters. Please see the linked CVE ID for the latest information on affected versions: * https://www.cve.org/CVERecord?id=CVE-2026-0672 * https://github.com/python/cpython/pull/143920

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[CVE-2025-15367] POP3 command injection in user-controlled commands
by Seth Larson Jan. 20, 2026

Jan. 20, 2026

There is a MEDIUM severity vulnerability affecting CPython. The poplib module, when passed a user-controlled command, can have additional commands injected using newlines. Mitigation rejects commands containing control characters. Please see the linked CVE ID for the latest information on affected versions: * https://www.cve.org/CVERecord?id=CVE-2025-15367 * https://github.com/python/cpython/pull/143924

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[CVE-2025-15366] IMAP command injection in user-controlled commands
by Seth Larson Jan. 20, 2026

Jan. 20, 2026

There is a MEDIUM severity vulnerability affecting CPython. The imaplib module, when passed a user-controlled command, can have additional commands injected using newlines. Mitigation rejects commands containing control characters. Please see the linked CVE ID for the latest information on affected versions: * https://www.cve.org/CVERecord?id=CVE-2025-15366 * https://github.com/python/cpython/pull/143922

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[CVE-2025-15282] Header injection via newlines in data URL mediatype
by Seth Larson Jan. 20, 2026

Jan. 20, 2026

There is a MEDIUM severity vulnerability affecting CPython. User-controlled data URLs parsed by urllib.request.DataHandler allow injecting headers through newlines in the data URL mediatype. Please see the linked CVE ID for the latest information on affected versions: * https://www.cve.org/CVERecord?id=CVE-2025-15282 * https://github.com/python/cpython/pull/143926

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Title: [CVE-2026-0865] wsgiref.headers.Headers allows header newline injection
by Seth Larson Jan. 20, 2026

Jan. 20, 2026

There is a MEDIUM severity vulnerability affecting CPython. User-controlled header names and values containing newlines can allow injecting HTTP headers. Please see the linked CVE ID for the latest information on affected versions: https://www.cve.org/CVERecord?id=CVE-2026-0865 https://github.com/python/cpython/pull/143917

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[CVE-2025-11468] Folding email comments of unfoldable characters doesn't preserve parenthesis
by Seth Larson Jan. 20, 2026

Jan. 20, 2026

There is a MEDIUM severity vulnerability affecting CPython. When folding a long comment in an email header containing exclusively unfoldable characters, the parenthesis would not be preserved. This could be used for injecting headers into email messages where addresses are user-controlled and not sanitized. Please see the linked CVE ID for the latest information on affected versions: * https://www.cve.org/CVERecord?id=CVE-2025-11468 * https://github.com/python/cpython/pull/143936

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[CVE-2025-12084] Quadratic complexity in node ID cache clearing
by Seth Larson Dec. 3, 2025

Dec. 3, 2025

There is a MEDIUM severity vulnerability affecting CPython. When building nested elements using xml.dom.minidom methods such as appendChild() that have a dependency on _clear_id_cache() the algorithm is quadratic. Availability can be impacted when building excessively nested documents. Please see the linked CVE ID for the latest information on affected versions: * https://www.cve.org/CVERecord?id=CVE-2025-12084 * https://github.com/python/cpython/pull/142146

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