CVE-2026-17084 (GCVE-0-2026-17084)
Vulnerability from cvelistv5 – Published: 2026-08-18 13:57 – Updated: 2026-08-18 14:05
VLAI
EPSS
VEX
Title
stringprep.map_table_b2() deviates from RFC 3454 Table B.2
Summary
The "stringprep" module didn't process characters from RFC 3454 tables
B.2 or B.3 correctly: the latest Unicode codepoint attributes were used
instead of the specified Unicode 3.2.0. This behavior would cause
mismatches when processing domain names using IDNA 2003 (the "idna"
codec) and the in_table_b2() function of the "stringprep" module. This
only affects domain names containing characters that were not previously
registered or had their Unicode attributes such as case-folding
behavior updated since Unicode 3.2.0.
Severity
Assigner
References
3 references
| URL | Tags |
|---|---|
| https://github.com/python/cpython/pull/155293 | patch |
| https://github.com/python/cpython/issues/155292 | issue-tracking |
| https://mail.python.org/archives/list/security-an… | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Python Software Foundation | CPython |
Affected:
0 , < 3.16.0
(python)
|
guessed |
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"modules": [
"stringprep",
"idna"
],
"product": "CPython",
"repo": "https://github.com/python/cpython",
"vendor": "Python Software Foundation",
"versions": [
{
"lessThan": "3.16.0",
"status": "affected",
"version": "0",
"versionType": "python"
}
]
}
],
"credits": [
{
"lang": "en",
"type": "reporter",
"value": "Bitshift (https://github.com/TheShiftedBit)"
},
{
"lang": "en",
"type": "coordinator",
"value": "Seth Larson (https://github.com/sethmlarson)"
},
{
"lang": "en",
"type": "remediation developer",
"value": "Stan Ulbrych (https://github.com/StanFromIreland)"
},
{
"lang": "en",
"type": "remediation reviewer",
"value": "Marc-Andre Lemburg (https://github.com/malemburg)"
},
{
"lang": "en",
"type": "remediation reviewer",
"value": "Petr Viktorin (https://github.com/encukou)"
}
],
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "The \"stringprep\" module didn\u0027t process characters from RFC 3454 tables \nB.2 or B.3 correctly: the latest Unicode codepoint attributes were used \ninstead of the specified Unicode 3.2.0. This behavior would cause \nmismatches when processing domain names using IDNA 2003 (the \"idna\" \ncodec) and the in_table_b2() function of the \"stringprep\" module. This \nonly affects domain names containing characters that were not previously\n registered or had their Unicode attributes such as case-folding \nbehavior updated since Unicode 3.2.0."
}
],
"value": "The \"stringprep\" module didn\u0027t process characters from RFC 3454 tables \nB.2 or B.3 correctly: the latest Unicode codepoint attributes were used \ninstead of the specified Unicode 3.2.0. This behavior would cause \nmismatches when processing domain names using IDNA 2003 (the \"idna\" \ncodec) and the in_table_b2() function of the \"stringprep\" module. This \nonly affects domain names containing characters that were not previously\n registered or had their Unicode attributes such as case-folding \nbehavior updated since Unicode 3.2.0."
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 6,
"baseSeverity": "MEDIUM",
"exploitMaturity": "NOT_DEFINED",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "PASSIVE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "HIGH",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-18T14:05:20.667Z",
"orgId": "28c92f92-d60d-412d-b760-e73465c3df22",
"shortName": "PSF"
},
"references": [
{
"tags": [
"patch"
],
"url": "https://github.com/python/cpython/pull/155293"
},
{
"tags": [
"issue-tracking"
],
"url": "https://github.com/python/cpython/issues/155292"
},
{
"tags": [
"vendor-advisory"
],
"url": "https://mail.python.org/archives/list/security-announce@python.org/thread/EUHHTC6EV7HCLSUHP25C5VHSV4V2MUZN/"
}
],
"source": {
"discovery": "UNKNOWN"
},
"title": "stringprep.map_table_b2() deviates from RFC 3454 Table B.2",
"x_generator": {
"engine": "Vulnogram 0.6.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "28c92f92-d60d-412d-b760-e73465c3df22",
"assignerShortName": "PSF",
"cveId": "CVE-2026-17084",
"datePublished": "2026-08-18T13:57:31.876Z",
"dateReserved": "2026-07-24T14:36:15.943Z",
"dateUpdated": "2026-08-18T14:05:20.667Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"nvd": "{\"cve\":{\"id\":\"CVE-2026-17084\",\"sourceIdentifier\":\"cna@python.org\",\"published\":\"2026-08-18T14:16:56.290\",\"lastModified\":\"2026-08-18T15:04:46.610\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"The \\\"stringprep\\\" module didn\u0027t process characters from RFC 3454 tables \\nB.2 or B.3 correctly: the latest Unicode codepoint attributes were used \\ninstead of the specified Unicode 3.2.0. This behavior would cause \\nmismatches when processing domain names using IDNA 2003 (the \\\"idna\\\" \\ncodec) and the in_table_b2() function of the \\\"stringprep\\\" module. This \\nonly affects domain names containing characters that were not previously\\n registered or had their Unicode attributes such as case-folding \\nbehavior updated since Unicode 3.2.0.\"}],\"affected\":[{\"source\":\"cna@python.org\",\"affectedData\":[{\"vendor\":\"Python Software Foundation\",\"product\":\"CPython\",\"defaultStatus\":\"unaffected\",\"repo\":\"https://github.com/python/cpython\",\"versions\":[{\"version\":\"0\",\"lessThan\":\"3.16.0\",\"versionType\":\"python\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"cna@python.org\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"4.0\",\"vectorString\":\"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X\",\"baseScore\":6.0,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"attackRequirements\":\"PRESENT\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"PASSIVE\",\"vulnConfidentialityImpact\":\"NONE\",\"vulnIntegrityImpact\":\"HIGH\",\"vulnAvailabilityImpact\":\"NONE\",\"subConfidentialityImpact\":\"NONE\",\"subIntegrityImpact\":\"NONE\",\"subAvailabilityImpact\":\"NONE\",\"exploitMaturity\":\"NOT_DEFINED\",\"confidentialityRequirement\":\"NOT_DEFINED\",\"integrityRequirement\":\"NOT_DEFINED\",\"availabilityRequirement\":\"NOT_DEFINED\",\"modifiedAttackVector\":\"NOT_DEFINED\",\"modifiedAttackComplexity\":\"NOT_DEFINED\",\"modifiedAttackRequirements\":\"NOT_DEFINED\",\"modifiedPrivilegesRequired\":\"NOT_DEFINED\",\"modifiedUserInteraction\":\"NOT_DEFINED\",\"modifiedVulnConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedVulnIntegrityImpact\":\"NOT_DEFINED\",\"modifiedVulnAvailabilityImpact\":\"NOT_DEFINED\",\"modifiedSubConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedSubIntegrityImpact\":\"NOT_DEFINED\",\"modifiedSubAvailabilityImpact\":\"NOT_DEFINED\",\"Safety\":\"NOT_DEFINED\",\"Automatable\":\"NOT_DEFINED\",\"Recovery\":\"NOT_DEFINED\",\"valueDensity\":\"NOT_DEFINED\",\"vulnerabilityResponseEffort\":\"NOT_DEFINED\",\"providerUrgency\":\"NOT_DEFINED\"}}]},\"references\":[{\"url\":\"https://github.com/python/cpython/issues/155292\",\"source\":\"cna@python.org\"},{\"url\":\"https://github.com/python/cpython/pull/155293\",\"source\":\"cna@python.org\"},{\"url\":\"https://mail.python.org/archives/list/security-announce@python.org/thread/EUHHTC6EV7HCLSUHP25C5VHSV4V2MUZN/\",\"source\":\"cna@python.org\"}]}}"
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
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.
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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.
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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