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    CVE-2026-0865

    User-controlled header names and values containing newlines can allow injecting HTTP headers.

    Published:Jan 20, 2026
    Last Modified:Apr 16, 2026
    EPS:Jan 20, 2026
    EPSS Score:0.00132
    CVSS Score:4.5

    Affected Products

    Vendor
    Python
    Product
    Cpython

    Exploits

    No exploit reference

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-10 Buffer Overflow via Environment Variables
    CAPEC-101 Server Side Include (SSI) Injection
    CAPEC-105 HTTP Request Splitting
    CAPEC-108 Command Line Execution through SQL Injection
    CAPEC-120 Double Encoding
    CAPEC-13 Subverting Environment Variable Values
    CAPEC-135 Format String Injection
    CAPEC-14 Client-side Injection-induced Buffer Overflow
    CAPEC-24 Filter Failure through Buffer Overflow
    CAPEC-250 XML Injection
    CAPEC-267 Leverage Alternate Encoding
    CAPEC-273 HTTP Response Smuggling
    CAPEC-28 Fuzzing
    CAPEC-3 Using Leading 'Ghost' Character Sequences to Bypass Input Filters
    CAPEC-34 HTTP Response Splitting
    CAPEC-42 MIME Conversion
    CAPEC-43 Exploiting Multiple Input Interpretation Layers
    CAPEC-45 Buffer Overflow via Symbolic Links
    CAPEC-46 Overflow Variables and Tags
    CAPEC-47 Buffer Overflow via Parameter Expansion
    CAPEC-51 Poison Web Service Registry
    CAPEC-52 Embedding NULL Bytes
    CAPEC-53 Postfix, Null Terminate, and Backslash
    CAPEC-6 Argument Injection
    CAPEC-64 Using Slashes and URL Encoding Combined to Bypass Validation Logic
    CAPEC-67 String Format Overflow in syslog()
    CAPEC-7 Blind SQL Injection
    CAPEC-71 Using Unicode Encoding to Bypass Validation Logic
    CAPEC-72 URL Encoding
    CAPEC-76 Manipulating Web Input to File System Calls
    CAPEC-78 Using Escaped Slashes in Alternate Encoding
    CAPEC-79 Using Slashes in Alternate Encoding
    CAPEC-8 Buffer Overflow in an API Call
    CAPEC-80 Using UTF-8 Encoding to Bypass Validation Logic
    CAPEC-83 XPath Injection
    CAPEC-84 XQuery Injection
    CAPEC-9 Buffer Overflow in Local Command-Line Utilities

    Related CVEs

    CVE-2026-15310 (CVSS 2.1) — When decompressing crafted zip files using the bzip/LZMA/Zstandard compressions, Python could use an attacke…
    CVE-2026-19672 (CVSS 6.3) — The tarfile module's tar and data extraction filters created directories outside the destination for members…
    CVE-2026-15806 (CVSS 6) — The HTTPPasswordMgr class in the urllib.request module, along with its subclasses HTTPPasswordMgrWithDefaultRe…
    CVE-2026-17084 (CVSS 6) — The "stringprep" module didn't process characters from RFC 3454 tables B.2 or B.3 correctly: the latest Unico…
    CVE-2026-18503 (CVSS 2.4) — Attacker-controlled CSV samples can trigger super-linear regular-expression work during dialect sniffing and …
    CVE-2026-6879 (CVSS 2) — `Element.findall()` and fully-consumed `Element.iterfind()` exhibit `O(n^2)` time complexity when using XPath …
    CVE-2026-15308 (CVSS 8.7) — The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated untermi…
    CVE-2026-4360 (CVSS 2) — In the Tarfile.extract() function, the filter parameter is not passed properly when extracting hardlinks. An a…
    CVE-2026-11972 (CVSS 8.2) — When using the "tarfile" module with a file opened in "streaming mode" (mode="r|") the tarfile module did not …
    CVE-2026-0864 (CVSS 4.1) — When using the "configparser" module to write configuration files containing multi-line text values with carri…

    References

    https://github.com/python/cpython/commit/22e4d55285cee52bc4dbe061324e5f30bd4dee58
    https://github.com/python/cpython/commit/23e3c0ae867cca0130e441e776c9955b9027c510
    https://github.com/python/cpython/commit/286e3ac39984fe85a17f4ab39c64d382137aae5f
    https://github.com/python/cpython/commit/2f840249550e082dc351743f474ba56da10478d2
    https://github.com/python/cpython/commit/4802b96a2cde58570c24c13ef3289490980961c5
    https://github.com/python/cpython/commit/66da7bf6fe7b81e3ecc9c0a25bd47d4616c8d1a6
    https://github.com/python/cpython/commit/83ecd18779f286d872f68bfce175651e407d9fff
    https://github.com/python/cpython/commit/8bb044d29310bb05d15086cdaa8bf64867d61a97
    https://github.com/python/cpython/commit/bfba660085767f8c2d582134e9d511a85eda04cf
    https://github.com/python/cpython/commit/c592227ffb48679af9845a45dbb0875d975bb219
    https://github.com/python/cpython/commit/e4846a93ac07a8ae9aa18203af0dd13d6e7a6995
    https://github.com/python/cpython/commit/f7fceed79ca1bceae8dbe5ba5bc8928564da7211
    https://github.com/python/cpython/issues/143916
    https://github.com/python/cpython/pull/143917
    https://mail.python.org/archives/list/[email protected]/thread/BJ6QPHNSHJTS3A7CFV6IBMCAP2DWRVNT/

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High