175 lines
12 KiB
JSON
175 lines
12 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2026-16760",
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"assignerOrgId": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082",
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"state": "PUBLISHED",
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"assignerShortName": "BombadilSystems",
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"dateReserved": "2026-07-23T14:00:36.878Z",
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"datePublished": "2026-10-30T21:16:31.353Z",
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"dateUpdated": "2026-11-06T16:01:12.427Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082",
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"shortName": "BombadilSystems",
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"dateUpdated": "2026-10-30T21:16:31.353Z"
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},
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"title": "Fickling check_safety() bypass: likely_safe_imports grants module-origin trust to unvalidated standard library callables",
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"problemTypes": [
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{
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"descriptions": [
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{
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"lang": "en",
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"cweId": "CWE-693",
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"description": "CWE-693 Protection Mechanism Failure",
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"type": "CWE"
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}
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]
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},
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{
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"descriptions": [
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{
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"lang": "en",
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"cweId": "CWE-502",
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"description": "CWE-502 Deserialization of Untrusted Data",
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"type": "CWE"
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}
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]
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}
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],
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"impacts": [
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{
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"descriptions": [
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{
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"lang": "en",
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"value": "An attacker can craft a malicious pickle that invokes a dangerous callable imported from a standard library module not present in UNSAFE_IMPORTS. The name is added to likely_safe_imports by _process_import(), causing OvertlyBadEvals to skip the call, so check_safety() returns LIKELY_SAFE and fickling.load() proceeds to deserialize the payload. This yields arbitrary code execution via dataclasses._create_fn or mailcap.findmatch on Python versions through 3.12, and arbitrary file write with attacker-controlled content via readline.write_history_file on POSIX platforms across supported Python versions. Because the flaw is in the module-origin trust model rather than in any specific module list, adding the demonstrated modules to UNSAFE_IMPORTS does not address the root cause; additional dangerous callables remain reachable through other non-blocked standard library modules."
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}
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]
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}
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],
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"affected": [
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{
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"vendor": "trailofbits",
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"product": "fickling",
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"collectionURL": "https://pypi.org/project/fickling/",
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"packageName": "fickling",
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"versions": [
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{
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"status": "affected",
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"version": "0",
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"lessThanOrEqual": "0.1.12",
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"versionType": "custom"
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}
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],
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"defaultStatus": "unaffected"
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}
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],
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"descriptions": [
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{
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"lang": "en",
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"value": "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 3.12 (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.",
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"supportingMedia": [
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{
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"type": "text/html",
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"base64": false,
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"value": "<p>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 3.12 (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.</p>"
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}
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]
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}
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],
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"references": [
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{
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"url": "https://bombadil.systems/advisories.html",
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"name": "Bombadil Systems advisory listing"
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},
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{
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"url": "https://pypi.org/project/fickling/0.1.12/",
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"name": "fickling 0.1.12 on PyPI"
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},
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{
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"url": "https://github.com/trailofbits/fickling",
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"name": "fickling source repository"
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},
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{
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"url": "https://github.com/trailofbits/fickling/commit/d011709",
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"name": "Vendor remediation merge commit d011709 (adds readline, dataclasses, and mailcap to UNSAFE_IMPORTS on master; the module-origin trust root cause remains)"
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}
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],
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"metrics": [
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{
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"format": "CVSS",
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"scenarios": [
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{
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"lang": "en",
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"value": "GENERAL"
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}
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],
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"cvssV3_1": {
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"version": "3.1",
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"attackVector": "NETWORK",
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"attackComplexity": "LOW",
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"privilegesRequired": "NONE",
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"userInteraction": "REQUIRED",
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"scope": "UNCHANGED",
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"confidentialityImpact": "HIGH",
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"integrityImpact": "HIGH",
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"availabilityImpact": "HIGH",
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"baseSeverity": "HIGH",
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"baseScore": 8.8,
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"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"
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}
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}
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],
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"credits": [
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{
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"lang": "en",
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"value": "Christopher Aziz (Bombadil Systems LLC)",
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"type": "finder"
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}
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],
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"source": {
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"discovery": "UNKNOWN"
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},
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"x_generator": {
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"engine": "Vulnogram 1.0.5"
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}
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},
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"adp": [
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{
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"metrics": [
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{
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"other": {
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"type": "ssvc",
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"content": {
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"timestamp": "2026-11-06T16:00:50.929044Z",
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"id": "CVE-2026-16760",
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"options": [
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{
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"Exploitation": "none"
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},
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{
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"Automatable": "no"
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},
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{
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"Technical Impact": "total"
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}
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],
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"role": "CISA Coordinator",
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"version": "2.0.3"
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}
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}
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}
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],
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"title": "CISA ADP Vulnrichment",
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"providerMetadata": {
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"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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"shortName": "CISA-ADP",
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"dateUpdated": "2026-11-06T16:01:12.427Z"
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}
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}
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]
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}
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} |