Red Hat Security Advisory: python3.12 security update

Fixed packages 13

Vulnerabilities 12

• Critical 9.1
  CVE-2026-6100

  Use-after-free in lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile after re-use under memory pressure

  Use-after-free (UAF) was possible in the `lzma.LZMADecompressor`, `bz2.BZ2Decompressor`, and `gzip.GzipFile` when a memory allocation fails with a `MemoryError` and the decompression instance is re-used. This scenario can be triggered if the process is under …

  Python Software Foundation CPython python3.4 python3.5 Debian Ubuntu Azure Linux Alpine Wolfi
  Apr 13, 2026
• High 7.5
  CVE-2025-59375

  libexpat in Expat before 2.7.2 allows attackers to trigger large dynamic memory allocations via a small document that i…

  libexpat project libexpat thunderbird firefox-esr Debian Ubuntu Azure Linux Alpine Wolfi
  Sep 15, 2025
• High 7.0
  CVE-2026-4519

  webbrowser.open() allows leading dashes in URLs

  The webbrowser.open() API would accept leading dashes in the URL which could be handled as command line options for certain web browsers. New behavior rejects leading dashes. Users are recommended to sanitize URLs prior to passing to webbrowser.open().

  Python Software Foundation CPython python3.4 python3.5 Debian Ubuntu Azure Linux Alpine Wolfi
  Mar 20, 2026
• High 7.0
  CVE-2026-4786

  Incomplete mitigation of CVE-2026-4519, %action expansion for command injection to webbrowser.open()

  Mitgation of CVE-2026-4519 was incomplete. If the URL contained "%action" the mitigation could be bypassed for certain browser types the "webbrowser.open()" API could have commands injected into the underlying shell. See CVE-2026-4519 for details.

  Python Software Foundation CPython python3.4 python3.5 Debian Ubuntu Azure Linux Alpine Wolfi
  Apr 13, 2026
• Medium 6.0
  CVE-2025-15282

  Header injection via newlines in data URL mediatype

  User-controlled data URLs parsed by urllib.request.DataHandler allow injecting headers through newlines in the data URL mediatype.

  Python Software Foundation CPython python3.4 python3.5 Debian Ubuntu Wolfi
  Jan 20, 2026
• Medium 6.0
  CVE-2026-0672

  Header injection in http.cookies.Morsel

  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.

  Python Software Foundation CPython python3.4 python3.5 Debian Ubuntu Azure Linux Wolfi
  Jan 20, 2026
• Medium 6.0
  CVE-2026-3644

  Incomplete control character validation in http.cookies

  The fix for CVE-2026-0672, which rejected control characters in http.cookies.Morsel, was incomplete. The Morsel.update(), |= operator, and unpickling paths were not patched, allowing control characters to bypass input validation. Additionally, BaseCookie.js_o…

  Python Software Foundation CPython python3.4 python3.5 Debian Ubuntu Azure Linux Alpine Wolfi
  Mar 16, 2026
• Medium 6.0
  CVE-2026-4224

  Stack overflow parsing XML with deeply nested DTD content models

  When an Expat parser with a registered ElementDeclHandler parses an inline document type definition containing a deeply nested content model a C stack overflow occurs.

  Python Software Foundation CPython python3.4 python3.5 Debian Ubuntu Azure Linux Alpine Wolfi
  Mar 16, 2026
• Medium 5.7
  CVE-2026-1502

  HTTP client proxy tunnel headers not validated for CR/LF

  CR/LF bytes were not rejected by HTTP client proxy tunnel headers or host.

  Python Software Foundation CPython python3.4 python3.5 Debian Ubuntu Azure Linux Alpine Wolfi
  Apr 10, 2026
• Medium 5.7
  CVE-2026-2297

  SourcelessFileLoader does not use io.open_code()

  The import hook in CPython that handles legacy *.pyc files (SourcelessFileLoader) is incorrectly handled in FileLoader (a base class) and so does not use io.open_code() to read the .pyc files. sys.audit handlers for this audit event therefore do not fire.

  Python Software Foundation CPython tensorflow python3.8 Debian Ubuntu Azure Linux Alpine Wolfi
  Mar 4, 2026
• Low 2.1
  CVE-2025-13837

  Out-of-memory when loading Plist

  When loading a plist file, the plistlib module reads data in size specified by the file itself, meaning a malicious file can cause OOM and DoS issues

  Python Software Foundation CPython python3.4 python3.5 Debian Ubuntu Azure Linux Wolfi
  Dec 1, 2025
• Low 1.8
  CVE-2025-6075

  Quadratic complexity in os.path.expandvars() with user-controlled template

  If the value passed to os.path.expandvars() is user-controlled a performance degradation is possible when expanding environment variables.

  Python Software Foundation CPython python3.4 python3.5 Debian Ubuntu Azure Linux Wolfi
  Oct 31, 2025

References

• article
  https://access.redhat.com/security/updates/classification/#important
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2395108
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2408891
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2418084
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2431366
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2431374
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2444691
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2448168
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2448181
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2449649
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2457409
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2457932
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2458049
• advisory
  https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_19177.json
• report
  https://access.redhat.com/security/cve/CVE-2025-6075
• advisory
  https://www.cve.org/CVERecord?id=CVE-2025-6075
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2025-6075
• article
  https://github.com/python/cpython/issues/136065
• article
  https://mail.python.org/archives/list/security-announce@python.org/thread/IUP5QJ6D4KK6ULHOMPC7DPNKRYQTQNLA/
• report
  https://access.redhat.com/security/cve/CVE-2025-13837
• advisory
  https://www.cve.org/CVERecord?id=CVE-2025-13837
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2025-13837
• article
  https://github.com/python/cpython/issues/119342
• article
  https://github.com/python/cpython/pull/119343
• report
  https://access.redhat.com/security/cve/CVE-2025-15282
• advisory
  https://www.cve.org/CVERecord?id=CVE-2025-15282
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2025-15282
• article
  https://github.com/python/cpython/issues/143925
• article
  https://github.com/python/cpython/pull/143926
• article
  https://mail.python.org/archives/list/security-announce@python.org/thread/X66HL7SISGJT33J53OHXMZT4DFLMHVKF/
• report
  https://access.redhat.com/security/cve/CVE-2025-59375
• advisory
  https://www.cve.org/CVERecord?id=CVE-2025-59375
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2025-59375
• article
  https://www.mozilla.org/security/advisories/mfsa2026-22/#CVE-2025-59375
• article
  https://www.mozilla.org/security/advisories/mfsa2026-24/#CVE-2025-59375
• report
  https://access.redhat.com/security/cve/CVE-2026-0672
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-0672
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-0672
• article
  https://github.com/python/cpython/issues/143919