ALPINE-CVE-2021-28957
Record from OSV · Published March 21, 2021
An XSS vulnerability was discovered in python-lxml's clean module versions before 4.6.3. When disabling the safe_attrs_only and forms arguments, the Cleaner class does not remove the formaction attribute allowing for JS to bypass the sanitizer. A remote attacker could exploit this flaw to run arbitrary JS code on users who interact with incorrectly sanitized HTML. This issue is patched in lxml 4.6.3.
Fixed versions
Upgrade to a fixed version or later. Language registries are listed first, then Linux distributions, then vendor products.
| Package | Ecosystem | Fixed in |
|---|---|---|
| py3-lxml | Alpine:v3.16 | 4.6.3-r0 |
| py3-lxml | Alpine:v3.20 | 4.6.3-r0 |
| py3-lxml | Alpine:v3.21 | 4.6.3-r0 |
| py3-lxml | Alpine:v3.19 | 4.6.3-r0 |
| py3-lxml | Alpine:v3.18 | 4.6.3-r0 |
| py3-lxml | Alpine:v3.22 | 4.6.3-r0 |
| py3-lxml | Alpine:v3.17 | 4.6.3-r0 |
| py3-lxml | Alpine:v3.23 | 4.6.3-r0 |
| py3-lxml | Alpine:v3.24 | 4.6.3-r0 |
Risk scores
Affected products
| Vendor | Product | Versions |
|---|---|---|
| Alpine:v3.16 | py3-lxml | 4.2.4-r0, 4.4.1-r0, 4.6.2-r0 |
| Alpine:v3.20 | py3-lxml | 2.2.8-r0, 0, 2.2.6-r0 |
| Alpine:v3.21 | py3-lxml | 4.4.0-r0, 4.1.0-r1, 3.6.4-r0 |
| Alpine:v3.19 | py3-lxml | 2.2.6-r0, 0, 2.2.8-r0 |
| Alpine:v3.18 | py3-lxml | 4.1.0-r0, 3.6.4-r0, 4.4.1-r1 |
| Alpine:v3.22 | py3-lxml | 4.5.0-r0, 3.4.0-r0, 4.3.3-r0 |
| Alpine:v3.17 | py3-lxml | 0, 2.2.6-r0, 2.2.8-r0 |
| Alpine:v3.23 | py3-lxml | 3.8.0-r0, 0, 2.2.6-r0 |
| Alpine:v3.24 | py3-lxml | 0 |
Timeline
- Mar 21, 2021 CVE Published
- Jun 15, 2026 CVE Updated
- Aug 8, 2026 Distribution Patch
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