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Response snapshot Oct 30, 2026, 23:06 UTC

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VulnerabilityCVE-2026-16760

In Trail of Bits fickling through 0.1.12, the _process_import() method in fickle.py adds an imported name to the likely_safe_imports set whenever the source module is present in...

In Trail of Bits fickling through 0.1.12, the _process_import() method in fickle.py adds an imported name to the likely_safe_imports set whenever the source module is present in sys.

At a glance

Exploited
Not known
Severity
8.8 High (CVSS 3.1)
Chance of exploitation
Not estimated
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-16760 (opens a new tab)

What happened

In Trail of Bits fickling through 0.1.12, the _process_import() method in fickle.py adds an imported name to the likely_safe_imports set whenever the source module is present in sys.stdlib_module_names and the name is absent from the UNSAFE_IMPORTS denylist, without inspecting what the name resolves to or how it behaves. The OvertlyBadEvals analysis pass in analysis.

py then unconditionally skips any call whose function name appears in likely_safe_imports, including calls that would otherwise be flagged as overtly dangerous.

As a result, any callable reachable through a non-blocked standard library module inherits module-level trust regardless of its own behavior, and check_safety() returns LIKELY_SAFE with zero findings for pickle payloads that reach code execution or file write through such callables. Demonstrated primitives: dataclasses.

_create_fn, which passes an attacker-controlled function body to exec() and yields arbitrary code execution on Python 3.7 through 3.12 (the internal _create_fn function was removed in Python 3.13); mailcap.findmatch, which internally calls os.system() on a test command taken from an attacker-controlled caps dictionary, yielding arbitrary code execution on Python versions through 3.

Continue reading

12 (the mailcap module was removed in Python 3.13); and readline.add_history() followed by readline.write_history_file(), which writes attacker-controlled content to an arbitrary filesystem path (POSIX platforms, where the readline module is available). fickling.load() chains check_safety() into pickle.

loads() as an explicit security gate, so a LIKELY_SAFE verdict causes the payload to be deserialized and executed with the privileges of the victim process. The root cause is the inference of callable safety from module origin; it is independent of, and separately fixable from, the dotted qualname resolution weakness tracked as CVE-2026-118938, which this advisory does not address.

As of 2026-10-30 the three demonstrated modules were added to UNSAFE_IMPORTS on the vendor master branch (commit d011709) pending release; released versions through 0.1.12 remain affected, and the module-origin trust root cause persists, as demonstrated by the related CVE-2026-118938 remaining exploitable on that same build.

Scores and how they were measured

CVSS base severity

8.8

Version 3.1As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Sources

  1. Primary source

    NVD CVE-2026-16760 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 30). In Trail of Bits fickling through 0.1.12, the _process_import() method in fickle.py adds an imported name to the likely_safe_imports set whenever the source module is present in... (CVE-2026-16760). https://kevwire.com/record/CVE-2026-16760

MLA

"In Trail of Bits fickling through 0.1.12, the _process_import() method in fickle.py adds an imported name to the likely_safe_imports set whenever the source module is present in... (CVE-2026-16760)." KEVWire, 30 Oct. 2026, kevwire.com/record/CVE-2026-16760.

Chicago

KEVWire. "In Trail of Bits fickling through 0.1.12, the _process_import() method in fickle.py adds an imported name to the likely_safe_imports set whenever the source module is present in... (CVE-2026-16760)." Last modified October 30, 2026. https://kevwire.com/record/CVE-2026-16760.

Evidence summary (plain text)

In Trail of Bits fickling through 0.1.12, the _process_import() method in fickle.py adds an imported name to the likely_safe_imports set whenever the source module is present in... (Oct 30, 2026).
In Trail of Bits fickling through 0.1.12, the _process_import() method in fickle.py adds an imported name to the likely_safe_imports set whenever the source module is present in sys.stdlib_module_names and the name is absent from the UNSAFE_IMPORTS denylist, without inspecting what the name resolves to or how it behaves. The OvertlyBadEvals analysis pass in analysis.py then unconditionally skips any call whose function name appears in likely_safe_imports, including calls that would otherwise be flagged as overtly dangerous.
CVSS 8.8 (version 3.1; evidence as of Oct 30, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-16760).
Sources:
NVD CVE-2026-16760: https://nvd.nist.gov/vuln/detail/CVE-2026-16760
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T21:30:58.248Z&lastModEndDate=2026-10-30T23:05:57.023Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T20:56:01.746Z&lastModEndDate=2026-10-30T22:30:56.395Z&resultsPerPage=500&startIndex=0
Record ID: CVE-2026-16760.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 30, 2026, 23:05 UTC. Ingestion is not an independent editorial investigation.

NVD status: Received. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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Record details

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