GHSA-v92g-xgxw-vvmm
ADVISORY - githubSummary
Summary
TemplateLookup.get_template() is vulnerable to path traversal when a URI starts with // (e.g., //../../../secret.txt). The root cause is an inconsistency between two slash-stripping implementations:
Template.__init__strips one leading/usingif/sliceTemplateLookup.get_template()strips all leading/usingre.sub(r"^\/+", "")
When a URI like //../../../../etc/passwd is passed:
get_template()strips all/→../../../../etc/passwd→ file found viaposixpath.join(dir_, u)Template.__init__strips one/→/../../../../etc/passwd→normpath→/etc/passwd/etc/passwd.startswith(..) →False→ check bypassed
Impact
Arbitrary file read: any file readable by the process can be returned as rendered template content when an application passes untrusted input directly to TemplateLookup.get_template().
Note: this is exploitable at the library API level. HTTP-based exploitation is mitigated by Python's BaseHTTPRequestHandler which normalizes double-slash prefixes since CPython gh-87389. Applications using other HTTP servers that do not normalize paths may be affected.
Fix
Changed Template.__init__ to use lstrip("/") instead of stripping only a single leading slash, so both code paths handle leading slashes consistently.
Common Weakness Enumeration (CWE)
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
GitHub
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CVSS SCORE
6.3medium| Package | Type | OS Name | OS Version | Affected Ranges | Fix Versions |
|---|---|---|---|---|---|
| mako | pypi | - | - | <=1.3.10 | 1.3.11 |
CVSS:4 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 successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: A race condition must be won to successfully exploit the vulnerability. The successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker. The attack may need to be launched multiple times against a single target before being successful. Network injection. The attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
The attacker is unauthenticated 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 human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges.
There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System.
There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
There is no loss of integrity within the Vulnerable System.
There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
There is no impact to availability within the Vulnerable System.
There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.