CVE Feed

    Dashboard / CVE / CVE-2021-43818

    CVE-2021-43818

    lxml is a library for processing XML and HTML in the Python language. Prior to version 4.6.5, the HTML Cleaner in lxml.html lets certain crafted script content pass through, as well as script content in SVG files embedded using data URIs. Users that employ the HTML cleaner in a security relevant context should upgrade to lxml 4.6.5 to receive a patch. There are no known workarounds available.

    Published:Dec 12, 2021
    Last Modified:Dec 18, 2025
    EPS:Dec 13, 2021
    EPSS Score:0.02804
    CVSS Score:8.2

    Affected Products

    Vendor
    Debian
    Product
    Debian Linux
    Vendor
    Fedoraproject
    Product
    Fedora
    Vendor
    Lxml
    Product
    Lxml
    Vendor
    Netapp
    Product
    Hci Storage Node
    Vendor
    Netapp
    Product
    Hci Storage Node Firmware
    Vendor
    Netapp
    Product
    Solidfire
    Vendor
    Netapp
    Product
    Solidfire Enterprise Sds
    Vendor
    Oracle
    Product
    Communications Cloud Native Core Binding Support Function
    Vendor
    Oracle
    Product
    Communications Cloud Native Core Network Exposure Function
    Vendor
    Oracle
    Product
    Communications Cloud Native Core Policy
    Vendor
    Oracle
    Product
    Http Server
    Vendor
    Oracle
    Product
    Zfs Storage Appliance Kit
    Vendor
    Redhat
    Product
    Enterprise Linux
    Vendor
    Redhat
    Product
    Rhel Software Collections
    Vendor
    Redhat
    Product
    Satellite
    Vendor
    Redhat
    Product
    Satellite Capsule

    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-136 LDAP Injection
    CAPEC-14 Client-side Injection-induced Buffer Overflow
    CAPEC-15 Command Delimiters
    CAPEC-183 IMAP/SMTP Command Injection
    CAPEC-209 XSS Using MIME Type Mismatch
    CAPEC-24 Filter Failure through Buffer Overflow
    CAPEC-248 Command Injection
    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-40 Manipulating Writeable Terminal Devices
    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-588 DOM-Based XSS
    CAPEC-591 Reflected XSS
    CAPEC-592 Stored XSS
    CAPEC-6 Argument Injection
    CAPEC-63 Cross-Site Scripting (XSS)
    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-75 Manipulating Writeable Configuration Files
    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-85 AJAX Footprinting
    CAPEC-9 Buffer Overflow in Local Command-Line Utilities

    Related CVEs

    CVE-2026-77118 (CVSS 8.4) — A heap out-of-bounds write exists in the Photo CD (PCD) decoder of GraphicsMagick. In DecodeImage() (coders/pc…
    CVE-2026-56968 (CVSS 3.7) — GNU SASL before 2.2.4 lacks sanitization of a short challenge in _gsasl_ntlm_client_step in the NTLM client, w…
    CVE-2026-49975 (CVSS 7.5) — Memory Allocation with Excessive Size Value vulnerability in Apache HTTP Server's mod_http leads to denial of …
    CVE-2026-9256 (CVSS 9.2) — NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerabilit…
    CVE-2026-31431 (CVSS 7.8) — In the Linux kernel, the following vulnerability has been resolved: crypto: algif_aead - Revert to operating …
    CVE-2026-34757 (CVSS 5.1) — LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network …
    CVE-2026-4775 (CVSS 7.8) — A flaw was found in the libtiff library. A remote attacker could exploit a signed integer overflow vulnerabili…
    CVE-2025-63261 (CVSS 7.8) — AWStats 8.0 is vulnerable to Command Injection via the open function…
    CVE-2026-3497 (CVSS 6.9) — Vulnerability in the OpenSSH GSSAPI delta included in various Linux distributions. This vulnerability affects …
    CVE-2026-1940 (CVSS 5.1) — An incomplete fix for CVE-2024-47778 allows an out-of-bounds read in gst_wavparse_adtl_chunk() function. The p…

    References

    https://github.com/lxml/lxml/commit/12fa9669007180a7bb87d990c375cf91ca5b664a
    https://github.com/lxml/lxml/commit/a3eacbc0dcf1de1c822ec29fb7d090a4b1712a9c#diff-59130575b4fb2932c957db2922977d7d89afb0b2085357db1a14615a2fcad776
    https://github.com/lxml/lxml/commit/f2330237440df7e8f39c3ad1b1aa8852be3b27c0
    https://github.com/lxml/lxml/security/advisories/GHSA-55x5-fj6c-h6m8
    https://lists.debian.org/debian-lts-announce/2021/12/msg00037.html
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TUIS2KE3HZ2AAQKXFLTJFZPP2IFHJTC7/
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/V2XMOM5PFT6U5AAXY6EFNT5JZCKKHK2V/
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WZGNET2A4WGLSUXLBFYKNC5PXHQMI3I7/
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZQ4SPKJX3RRJK4UWA6FXCRHD2TVRQI44/
    https://security.gentoo.org/glsa/202208-06
    https://security.netapp.com/advisory/ntap-20220107-0005/
    https://www.debian.org/security/2022/dsa-5043
    https://www.oracle.com/security-alerts/cpuapr2022.html
    https://www.oracle.com/security-alerts/cpujul2022.html
    https://github.com/lxml/lxml/commit/12fa9669007180a7bb87d990c375cf91ca5b664a
    https://github.com/lxml/lxml/commit/a3eacbc0dcf1de1c822ec29fb7d090a4b1712a9c#diff-59130575b4fb2932c957db2922977d7d89afb0b2085357db1a14615a2fcad776
    https://github.com/lxml/lxml/commit/f2330237440df7e8f39c3ad1b1aa8852be3b27c0
    https://github.com/lxml/lxml/security/advisories/GHSA-55x5-fj6c-h6m8
    https://lists.debian.org/debian-lts-announce/2021/12/msg00037.html
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TUIS2KE3HZ2AAQKXFLTJFZPP2IFHJTC7/
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/V2XMOM5PFT6U5AAXY6EFNT5JZCKKHK2V/
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WZGNET2A4WGLSUXLBFYKNC5PXHQMI3I7/
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZQ4SPKJX3RRJK4UWA6FXCRHD2TVRQI44/
    https://security.gentoo.org/glsa/202208-06
    https://security.netapp.com/advisory/ntap-20220107-0005/
    https://www.debian.org/security/2022/dsa-5043
    https://www.oracle.com/security-alerts/cpuapr2022.html
    https://www.oracle.com/security-alerts/cpujul2022.html

    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