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ubuntucveUbuntu.comUB:CVE-2021-28957
HistoryMar 21, 2021 - 12:00 a.m.

CVE-2021-28957

2021-03-2100:00:00
ubuntu.com
ubuntu.com
24
python-lxml
cve-2021-28957
xss vulnerability
cleaner class
arbitrary js code
html sanitizer
remote attacker
patched
unix

CVSS2

4.3

Attack Vector

NETWORK

Attack Complexity

MEDIUM

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

PARTIAL

Availability Impact

NONE

AV:N/AC:M/Au:N/C:N/I:P/A:N

CVSS3

6.1

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

REQUIRED

Scope

CHANGED

Confidentiality Impact

LOW

Integrity Impact

LOW

Availability Impact

NONE

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

0.002

Percentile

61.6%

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.

Bugs

OSVersionArchitecturePackageVersionFilename
ubuntu18.04noarchlxml< 4.2.1-1ubuntu0.4UNKNOWN
ubuntu20.04noarchlxml< 4.5.0-1ubuntu0.3UNKNOWN
ubuntu20.10noarchlxml< 4.5.2-1ubuntu0.4UNKNOWN
ubuntu14.04noarchlxml< 3.3.3-1ubuntu0.2+esm3UNKNOWN
ubuntu16.04noarchlxml< 3.5.0-1ubuntu0.4UNKNOWN

CVSS2

4.3

Attack Vector

NETWORK

Attack Complexity

MEDIUM

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

PARTIAL

Availability Impact

NONE

AV:N/AC:M/Au:N/C:N/I:P/A:N

CVSS3

6.1

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

REQUIRED

Scope

CHANGED

Confidentiality Impact

LOW

Integrity Impact

LOW

Availability Impact

NONE

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

0.002

Percentile

61.6%