CVE-2021-43818
HIGHCVSS 7.1/10EPSS 2.46%
Last modified
CVE-2021-43818 is a high-severity vulnerability rated 7.1/10 on the CVSS scale. 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. EPSS estimates a 2.46% chance of exploitation in the next 30 days.
Description
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.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Lxml | Lxml | < 4.6.5 |
| Fedoraproject | Fedora | 34 |
| Fedoraproject | Fedora | 35 |
| Debian | Debian Linux | 9.0 |
| Debian | Debian Linux | 10.0 |
| Debian | Debian Linux | 11.0 |
| Netapp | Solidfire | All versions |
| Netapp | Solidfire Enterprise Sds | All versions |
| Netapp | Hci Storage Node Firmware | All versions |
| Oracle | Communications Cloud Native Core Binding Support Function | 22.1.3 |
| Oracle | Communications Cloud Native Core Network Exposure Function | 22.1.1 |
| Oracle | Communications Cloud Native Core Policy | 22.2.0 |
| Oracle | Http Server | 12.2.1.3.0 |
| Oracle | Http Server | 12.2.1.4.0 |
| Oracle | Zfs Storage Appliance Kit | 8.8 |
References
- https://github.com/lxml/lxml/commit/12fa9669007180a7bb87d990c375cf91ca5b664aPatch, Third Party Advisory
- https://github.com/lxml/lxml/commit/f2330237440df7e8f39c3ad1b1aa8852be3b27c0Patch, Third Party Advisory
- https://github.com/lxml/lxml/security/advisories/GHSA-55x5-fj6c-h6m8Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/12/msg00037.htmlMailing List, Third Party Advisory
- https://security.gentoo.org/glsa/202208-06Third Party Advisory
- https://security.netapp.com/advisory/ntap-20220107-0005/Third Party Advisory
- https://www.debian.org/security/2022/dsa-5043Third Party Advisory
- https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch, Third Party Advisory
- https://www.oracle.com/security-alerts/cpujul2022.htmlPatch, Third Party Advisory
- https://github.com/lxml/lxml/commit/12fa9669007180a7bb87d990c375cf91ca5b664aPatch, Third Party Advisory
- https://github.com/lxml/lxml/commit/f2330237440df7e8f39c3ad1b1aa8852be3b27c0Patch, Third Party Advisory
- https://github.com/lxml/lxml/security/advisories/GHSA-55x5-fj6c-h6m8Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/12/msg00037.htmlMailing List, Third Party Advisory
- https://security.gentoo.org/glsa/202208-06Third Party Advisory
- https://security.netapp.com/advisory/ntap-20220107-0005/Third Party Advisory
- https://www.debian.org/security/2022/dsa-5043Third Party Advisory
- https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch, Third Party Advisory
- https://www.oracle.com/security-alerts/cpujul2022.htmlPatch, Third Party Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is 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.
How severe is CVE-2021-43818?
CVE-2021-43818 has a CVSS score of 7.1/10 (HIGH severity). The EPSS model estimates a 2.46% probability of exploitation in the next 30 days.
How do I fix CVE-2021-43818?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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