CVE-2026-41066
ADVISORY - githubSummary
Impact
Using either of the two parsers in the default configuration (with resolve_entities=True) allows untrusted XML input to read local files.
Patches
lxml 6.1.0 changes the default to resolve_entities='internal', thus disallowing local file access by default.
Workarounds
Setting the resolve_entities option explicitly to resolve_entities='internal' or resolve_entities=False disables the local file access.
Resources
Original report: https://bugs.launchpad.net/lxml/+bug/2146291
The default option was changed to resolve_entities='internal' for the normal XML and HTML parsers in lxml 5.0. The default was not changed for iterparse() and ETCompatXMLParser() at the time. lxml 6.1 makes the safe option the default for all parsers.
Common Weakness Enumeration (CWE)
Improper Restriction of XML External Entity Reference
GitHub
3.9
CVSS SCORE
7.5high| Package | Type | OS Name | OS Version | Affected Ranges | Fix Versions |
|---|---|---|---|---|---|
| lxml | pypi | - | - | <6.1.0 | 6.1.0 |
CVSS:3 Severity and metrics
The CVSS metrics represent different qualitative aspects of a vulnerability that impact the overall score, as defined by the CVSS Specification.
The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone). One example of an Adjacent attack would be an ARP (IPv4) or neighbor discovery (IPv6) flood leading to a denial of service on the local LAN segment (e.g., CVE-2013-6014).
Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component.
The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
The vulnerable system can be exploited without interaction from any user.
An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
There is a total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
There is no loss of trust or accuracy within the impacted component.
There is no impact to availability within the impacted component.