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CVE-2026-118938
Published:October 30, 2026
Updated:November 04, 2026
In Trail of Bits fickling through 0.1.12, a pickle STACK_GLOBAL operand carrying a dotted qualname (for example "Values.read_file") is resolved by pickle's find_class through _getattribute to an arbitrary attribute path rather than to a module-level function. Fickling records only the leading component of the name in its import tracking and renders the operation as a plain import (for instance, 'python -m fickling' displays it as 'from optparse import Values.read_file'), so the trailing attribute reference is never analyzed as a call. The OvertlyBadEvals analysis pass does not flag it, and check_safety() returns LIKELY_SAFE with zero findings. This allows an attacker to reach a class method that performs code execution: optparse.Values.read_file executes exec(open(filename).read(), vars), achieving arbitrary code execution when the crafted pickle is loaded through fickling.load(), which chains check_safety() into pickle.loads() as an explicit security gate. optparse is present in all current CPython 3.x releases (deprecated as of Python 3.13, not removed). This weakness is in the resolution and analysis of dotted attribute-path names, and is distinct from and independently fixable from the module-origin trust weakness tracked as CVE-2026-16760: resolving or flagging dotted attribute-path imports closes this vector while leaving the module-level trust behavior unchanged. This bypass was verified to remain present on the vendor master branch at commit d011709 as of 2026-10-30, after the vendor's October blocklist additions and a new heuristic that flags private stdlib attributes; because the public class method Values.read_file is neither blocklisted nor flagged as a private attribute, it is not addressed by those remediations.
Additional Notes
The description of this vulnerability differs from MITRE.
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CVSS v4
Base Score:
8.7
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
PASSIVE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
HIGH
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
8.8
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Weakness Type (CWE)
Deserialization of Untrusted Data
Use of Incorrectly-Resolved Name or Reference
EPSS
Base Score:
0.48