Vulnerability-Lookup

FKIE_CVE-2026-118938

Vulnerability from fkie_nvd - Published: 2026-10-30 22:16 - Updated: 2026-10-30 22:16

Severity

8.8 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Summary

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.

References

	URL	Tags
	aa17e1a1-c329-4d6e-a1ed-8d0188aea082	https://bombadil.systems/advisories.html
	aa17e1a1-c329-4d6e-a1ed-8d0188aea082	https://github.com/trailofbits/fickling
	aa17e1a1-c329-4d6e-a1ed-8d0188aea082	https://github.com/trailofbits/fickling/commit/d011709
	aa17e1a1-c329-4d6e-a1ed-8d0188aea082	https://pypi.org/project/fickling/0.1.12/

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://pypi.org/project/fickling/",
          "defaultStatus": "affected",
          "packageName": "fickling",
          "product": "fickling",
          "repo": "https://github.com/trailofbits/fickling",
          "vendor": "trailofbits",
          "versions": [
            {
              "lessThanOrEqual": "0.1.12",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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\u0027s 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, \u0027python -m fickling\u0027 displays it as \u0027from optparse import Values.read_file\u0027), 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\u0027s 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."
    }
  ],
  "id": "CVE-2026-118938",
  "lastModified": "2026-10-30T22:16:54.020",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 8.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 5.9,
        "source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-10-30T22:16:54.020",
  "references": [
    {
      "source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082",
      "url": "https://bombadil.systems/advisories.html"
    },
    {
      "source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082",
      "url": "https://github.com/trailofbits/fickling"
    },
    {
      "source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082",
      "url": "https://github.com/trailofbits/fickling/commit/d011709"
    },
    {
      "source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082",
      "url": "https://pypi.org/project/fickling/0.1.12/"
    }
  ],
  "sourceIdentifier": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-502"
        },
        {
          "lang": "en",
          "value": "CWE-706"
        }
      ],
      "source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082",
      "type": "Secondary"
    }
  ]
}

CVE-2026-118938 (GCVE-0-2026-118938)

Vulnerability from cvelistv5 – Published: 2026-10-30 21:19 – Updated: 2026-10-30 21:19

Title

Fickling check_safety() bypass: dotted __qualname__ in STACK_GLOBAL resolves a class-method attribute path that evades call analysis

Summary

Severity

8.8 (High)


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

CWE

CWE-706 - Use of Incorrectly-Resolved Name or Reference
CWE-502 - Deserialization of Untrusted Data

Assigner

BombadilSystems CNA under the mitre root

CNA scorecard – unranked: 4 records in the last 180 days, 10 needed details

References

4 references

URL	Tags
https://bombadil.systems/advisories.html
https://pypi.org/project/fickling/0.1.12/
https://github.com/trailofbits/fickling
https://github.com/trailofbits/fickling/commit/d011709

Impacted products

1 product

Vendor	Product	Version
trailofbits	fickling	Affected: 0 , ≤ 0.1.12 (custom)

Date Public

2026-10-30 21:17

Credits

Christopher Aziz (Bombadil Systems LLC)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "collectionURL": "https://pypi.org/project/fickling/",
          "defaultStatus": "affected",
          "packageName": "fickling",
          "product": "fickling",
          "repo": "https://github.com/trailofbits/fickling",
          "vendor": "trailofbits",
          "versions": [
            {
              "lessThanOrEqual": "0.1.12",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Christopher Aziz (Bombadil Systems LLC)"
        }
      ],
      "datePublic": "2026-10-30T21:17:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cp\u003eIn 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\u0027s 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, \u0027python -m fickling\u0027 displays it as \u0027from optparse import Values.read_file\u0027), 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\u0027s 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.\u003c/p\u003e"
            }
          ],
          "value": "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\u0027s 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, \u0027python -m fickling\u0027 displays it as \u0027from optparse import Values.read_file\u0027), 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\u0027s 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."
        }
      ],
      "impacts": [
        {
          "descriptions": [
            {
              "lang": "en",
              "value": "An attacker can craft a malicious pickle whose STACK_GLOBAL operand encodes a dotted attribute path to a code-executing class method, such as optparse.Values.read_file. Fickling treats the dotted name as a single trusted import and does not analyze the resulting call, so check_safety() returns LIKELY_SAFE and fickling.load() deserializes the payload, executing attacker-controlled Python with the privileges of the victim process. The vector is independent of the specific contents of UNSAFE_IMPORTS; it stems from fickling resolving and recording dotted attribute-path names incorrectly, so denylisting individual modules does not address it."
            }
          ]
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
            "version": "3.1"
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          "scenarios": [
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      "problemTypes": [
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          "descriptions": [
            {
              "cweId": "CWE-706",
              "description": "CWE-706 Use of Incorrectly-Resolved Name or Reference",
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              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-502",
              "description": "CWE-502 Deserialization of Untrusted Data",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-30T21:19:13.015Z",
        "orgId": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082",
        "shortName": "BombadilSystems"
      },
      "references": [
        {
          "name": "Bombadil Systems advisory listing",
          "url": "https://bombadil.systems/advisories.html"
        },
        {
          "name": "fickling 0.1.12 on PyPI",
          "url": "https://pypi.org/project/fickling/0.1.12/"
        },
        {
          "name": "fickling source repository",
          "url": "https://github.com/trailofbits/fickling"
        },
        {
          "name": "Vendor remediation merge commit d011709 (does not address this vector; optparse.Values.read_file remains exploitable on master)",
          "url": "https://github.com/trailofbits/fickling/commit/d011709"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Fickling check_safety() bypass: dotted __qualname__ in STACK_GLOBAL resolves a class-method attribute path that evades call analysis",
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    "cveId": "CVE-2026-118938",
    "datePublished": "2026-10-30T21:19:13.015Z",
    "dateReserved": "2026-10-29T05:42:00.023Z",
    "dateUpdated": "2026-10-30T21:19:13.015Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Vulnerability timeline

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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