lxml 4.6.2 HTML5 html/defs.py action HTML injection

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
5.7$0-$5k0.00

Summaryinfo

A vulnerability was found in lxml 4.6.2. It has been rated as critical. This impacts an unknown function of the file html/defs.py of the component HTML5 Handler. The manipulation of the argument action leads to an unknown weakness. This vulnerability is documented as CVE-2021-28957. There is not any exploit available. It is suggested to install a patch to address this issue.

Detailsinfo

A vulnerability was found in lxml 4.6.2. It has been rated as critical. This issue affects an unknown function of the file html/defs.py of the component HTML5 Handler. The manipulation of the argument action with an unknown input leads to a unknown weakness. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. The impact remains unknown.

The weakness was released 03/21/2021. The advisory is shared at bugs.launchpad.net. The identification of this vulnerability is CVE-2021-28957. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1059.007 for this issue.

Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Name

Version

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.8
VulDB Meta Temp Score: 5.7

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 6.1
NVD Vector: 🔍

CVSSv2info

AVACAuCIA
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock

VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: HTML injection
CWE: CWE-79 / CWE-94 / CWE-74
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-DayUnlockUnlockUnlockUnlock
TodayUnlockUnlockUnlockUnlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔍

Patch: github.com

Timelineinfo

03/21/2021 🔍
03/21/2021 +0 days 🔍
03/21/2021 +0 days 🔍
12/18/2025 +1732 days 🔍

Sourcesinfo

Product: github.com

Advisory: bugs.launchpad.net
Status: Confirmed

CVE: CVE-2021-28957 (🔍)
GCVE (CVE): GCVE-0-2021-28957
GCVE (VulDB): GCVE-100-171521

Entryinfo

Created: 03/21/2021 18:08
Updated: 12/18/2025 00:23
Changes: 03/21/2021 18:08 (37), 04/03/2021 13:40 (2), 04/03/2021 13:44 (20), 12/18/2025 00:23 (22)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Discussion

No comments yet. Languages: en.

Please log in to comment.

◂ PreviousOverviewNext ▸

Want to know what is going to be exploited?

We predict KEV entries!