FKIE_CVE-2026-6253
Vulnerability from fkie_nvd - Published: 2026-05-13 13:01 - Updated: 2026-09-15 07:16
Severity
Summary
curl might erroneously pass on credentials for a first proxy to a second
proxy.
This can happen when the following conditions are true:
1. curl is setup to use specific different proxies for different URL schemes
2. the first proxy needs credentials
3. the second proxy uses no credentials
4. while using the first proxy (using say `http://`), curl is asked to follow
a redirect to a URL using another scheme (say `https://`), accessed using a
second, different, proxy
References
| URL | Tags | ||
|---|---|---|---|
| 2499f714-1537-4658-8207-48ae4bb9eae9 | https://curl.se/docs/CVE-2026-6253.html | Patch, Vendor Advisory | |
| 2499f714-1537-4658-8207-48ae4bb9eae9 | https://curl.se/docs/CVE-2026-6253.json | Vendor Advisory | |
| 2499f714-1537-4658-8207-48ae4bb9eae9 | https://hackerone.com/reports/3669637 | Exploit, Issue Tracking, Third Party Advisory | |
| af854a3a-2127-422b-91ae-364da2661108 | http://www.openwall.com/lists/oss-security/2026/04/29/11 | Mailing List, Patch, Third Party Advisory | |
| 134c704f-9b21-4f2e-91b3-4a467353bcc0 | https://hackerone.com/reports/3669637 | Exploit, Issue Tracking, Third Party Advisory |
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "curl",
"vendor": "curl",
"versions": [
{
"lessThan": "8.14.2",
"status": "affected",
"version": "7.14.1",
"versionType": "semver"
},
{
"lessThan": "8.16.1",
"status": "affected",
"version": "8.15.0",
"versionType": "semver"
},
{
"lessThan": "8.20.0",
"status": "affected",
"version": "8.17.0",
"versionType": "semver"
}
]
},
{
"defaultStatus": "unaffected",
"product": "curl",
"repo": "https://github.com/curl/curl.git",
"vendor": "curl",
"versions": [
{
"lessThan": "188c2f166a20fa97c2325b2da7d0e5cecc13725f",
"status": "affected",
"version": "3b60bb725913ce7339aefef0a14b12df4c24db60",
"versionType": "git"
}
]
},
{
"defaultStatus": "unaffected",
"product": "curl",
"vendor": "curl",
"versions": [
{
"status": "affected",
"version": "8.19.0"
},
{
"status": "affected",
"version": "8.18.0"
},
{
"status": "affected",
"version": "8.17.0"
},
{
"status": "affected",
"version": "8.16.0"
},
{
"status": "affected",
"version": "8.15.0"
},
{
"status": "affected",
"version": "8.14.1"
},
{
"status": "affected",
"version": "8.14.0"
},
{
"status": "affected",
"version": "8.13.0"
},
{
"status": "affected",
"version": "8.12.1"
},
{
"status": "affected",
"version": "8.12.0"
},
{
"status": "affected",
"version": "8.11.1"
},
{
"status": "affected",
"version": "8.11.0"
},
{
"status": "affected",
"version": "8.10.1"
},
{
"status": "affected",
"version": "8.10.0"
},
{
"status": "affected",
"version": "8.9.1"
},
{
"status": "affected",
"version": "8.9.0"
},
{
"status": "affected",
"version": "8.8.0"
},
{
"status": "affected",
"version": "8.7.1"
},
{
"status": "affected",
"version": "8.7.0"
},
{
"status": "affected",
"version": "8.6.0"
},
{
"status": "affected",
"version": "8.5.0"
},
{
"status": "affected",
"version": "8.4.0"
},
{
"status": "affected",
"version": "8.3.0"
},
{
"status": "affected",
"version": "8.2.1"
},
{
"status": "affected",
"version": "8.2.0"
},
{
"status": "affected",
"version": "8.1.2"
},
{
"status": "affected",
"version": "8.1.1"
},
{
"status": "affected",
"version": "8.1.0"
},
{
"status": "affected",
"version": "8.0.1"
},
{
"status": "affected",
"version": "8.0.0"
},
{
"status": "affected",
"version": "7.88.1"
},
{
"status": "affected",
"version": "7.88.0"
},
{
"status": "affected",
"version": "7.87.0"
},
{
"status": "affected",
"version": "7.86.0"
},
{
"status": "affected",
"version": "7.85.0"
},
{
"status": "affected",
"version": "7.84.0"
},
{
"status": "affected",
"version": "7.83.1"
},
{
"status": "affected",
"version": "7.83.0"
},
{
"status": "affected",
"version": "7.82.0"
},
{
"status": "affected",
"version": "7.81.0"
},
{
"status": "affected",
"version": "7.80.0"
},
{
"status": "affected",
"version": "7.79.1"
},
{
"status": "affected",
"version": "7.79.0"
},
{
"status": "affected",
"version": "7.78.0"
},
{
"status": "affected",
"version": "7.77.0"
},
{
"status": "affected",
"version": "7.76.1"
},
{
"status": "affected",
"version": "7.76.0"
},
{
"status": "affected",
"version": "7.75.0"
},
{
"status": "affected",
"version": "7.74.0"
},
{
"status": "affected",
"version": "7.73.0"
},
{
"status": "affected",
"version": "7.72.0"
},
{
"status": "affected",
"version": "7.71.1"
},
{
"status": "affected",
"version": "7.71.0"
},
{
"status": "affected",
"version": "7.70.0"
},
{
"status": "affected",
"version": "7.69.1"
},
{
"status": "affected",
"version": "7.69.0"
},
{
"status": "affected",
"version": "7.68.0"
},
{
"status": "affected",
"version": "7.67.0"
},
{
"status": "affected",
"version": "7.66.0"
},
{
"status": "affected",
"version": "7.65.3"
},
{
"status": "affected",
"version": "7.65.2"
},
{
"status": "affected",
"version": "7.65.1"
},
{
"status": "affected",
"version": "7.65.0"
},
{
"status": "affected",
"version": "7.64.1"
},
{
"status": "affected",
"version": "7.64.0"
},
{
"status": "affected",
"version": "7.63.0"
},
{
"status": "affected",
"version": "7.62.0"
},
{
"status": "affected",
"version": "7.61.1"
},
{
"status": "affected",
"version": "7.61.0"
},
{
"status": "affected",
"version": "7.60.0"
},
{
"status": "affected",
"version": "7.59.0"
},
{
"status": "affected",
"version": "7.58.0"
},
{
"status": "affected",
"version": "7.57.0"
},
{
"status": "affected",
"version": "7.56.1"
},
{
"status": "affected",
"version": "7.56.0"
},
{
"status": "affected",
"version": "7.55.1"
},
{
"status": "affected",
"version": "7.55.0"
},
{
"status": "affected",
"version": "7.54.1"
},
{
"status": "affected",
"version": "7.54.0"
},
{
"status": "affected",
"version": "7.53.1"
},
{
"status": "affected",
"version": "7.53.0"
},
{
"status": "affected",
"version": "7.52.1"
},
{
"status": "affected",
"version": "7.52.0"
},
{
"status": "affected",
"version": "7.51.0"
},
{
"status": "affected",
"version": "7.50.3"
},
{
"status": "affected",
"version": "7.50.2"
},
{
"status": "affected",
"version": "7.50.1"
},
{
"status": "affected",
"version": "7.50.0"
},
{
"status": "affected",
"version": "7.49.1"
},
{
"status": "affected",
"version": "7.49.0"
},
{
"status": "affected",
"version": "7.48.0"
},
{
"status": "affected",
"version": "7.47.1"
},
{
"status": "affected",
"version": "7.47.0"
},
{
"status": "affected",
"version": "7.46.0"
},
{
"status": "affected",
"version": "7.45.0"
},
{
"status": "affected",
"version": "7.44.0"
},
{
"status": "affected",
"version": "7.43.0"
},
{
"status": "affected",
"version": "7.42.1"
},
{
"status": "affected",
"version": "7.42.0"
},
{
"status": "affected",
"version": "7.41.0"
},
{
"status": "affected",
"version": "7.40.0"
},
{
"status": "affected",
"version": "7.39.0"
},
{
"status": "affected",
"version": "7.38.0"
},
{
"status": "affected",
"version": "7.37.1"
},
{
"status": "affected",
"version": "7.37.0"
},
{
"status": "affected",
"version": "7.36.0"
},
{
"status": "affected",
"version": "7.35.0"
},
{
"status": "affected",
"version": "7.34.0"
},
{
"status": "affected",
"version": "7.33.0"
},
{
"status": "affected",
"version": "7.32.0"
},
{
"status": "affected",
"version": "7.31.0"
},
{
"status": "affected",
"version": "7.30.0"
},
{
"status": "affected",
"version": "7.29.0"
},
{
"status": "affected",
"version": "7.28.1"
},
{
"status": "affected",
"version": "7.28.0"
},
{
"status": "affected",
"version": "7.27.0"
},
{
"status": "affected",
"version": "7.26.0"
},
{
"status": "affected",
"version": "7.25.0"
},
{
"status": "affected",
"version": "7.24.0"
},
{
"status": "affected",
"version": "7.23.1"
},
{
"status": "affected",
"version": "7.23.0"
},
{
"status": "affected",
"version": "7.22.0"
},
{
"status": "affected",
"version": "7.21.7"
},
{
"status": "affected",
"version": "7.21.6"
},
{
"status": "affected",
"version": "7.21.5"
},
{
"status": "affected",
"version": "7.21.4"
},
{
"status": "affected",
"version": "7.21.3"
},
{
"status": "affected",
"version": "7.21.2"
},
{
"status": "affected",
"version": "7.21.1"
},
{
"status": "affected",
"version": "7.21.0"
},
{
"status": "affected",
"version": "7.20.1"
},
{
"status": "affected",
"version": "7.20.0"
},
{
"status": "affected",
"version": "7.19.7"
},
{
"status": "affected",
"version": "7.19.6"
},
{
"status": "affected",
"version": "7.19.5"
},
{
"status": "affected",
"version": "7.19.4"
},
{
"status": "affected",
"version": "7.19.3"
},
{
"status": "affected",
"version": "7.19.2"
},
{
"status": "affected",
"version": "7.19.1"
},
{
"status": "affected",
"version": "7.19.0"
},
{
"status": "affected",
"version": "7.18.2"
},
{
"status": "affected",
"version": "7.18.1"
},
{
"status": "affected",
"version": "7.18.0"
},
{
"status": "affected",
"version": "7.17.1"
},
{
"status": "affected",
"version": "7.17.0"
},
{
"status": "affected",
"version": "7.16.4"
},
{
"status": "affected",
"version": "7.16.3"
},
{
"status": "affected",
"version": "7.16.2"
},
{
"status": "affected",
"version": "7.16.1"
},
{
"status": "affected",
"version": "7.16.0"
},
{
"status": "affected",
"version": "7.15.5"
},
{
"status": "affected",
"version": "7.15.4"
},
{
"status": "affected",
"version": "7.15.3"
},
{
"status": "affected",
"version": "7.15.2"
},
{
"status": "affected",
"version": "7.15.1"
},
{
"status": "affected",
"version": "7.15.0"
},
{
"status": "affected",
"version": "7.14.1"
}
]
}
],
"source": "2499f714-1537-4658-8207-48ae4bb9eae9"
}
],
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*",
"matchCriteriaId": "C839F5FA-8CCE-4F13-851D-E60E8EAAA08C",
"versionEndExcluding": "8.20.0",
"versionStartIncluding": "7.14.1",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "curl might erroneously pass on credentials for a first proxy to a second\nproxy.\n\nThis can happen when the following conditions are true:\n\n1. curl is setup to use specific different proxies for different URL schemes\n2. the first proxy needs credentials\n3. the second proxy uses no credentials\n4. while using the first proxy (using say `http://`), curl is asked to follow\n a redirect to a URL using another scheme (say `https://`), accessed using a\n second, different, proxy"
}
],
"id": "CVE-2026-6253",
"lastModified": "2026-09-15T07:16:29.073",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "HIGH",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 5.9,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"exploitabilityScore": 2.2,
"impactScore": 3.6,
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-6253",
"options": [
{
"exploitation": "poc"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-05-13T17:42:30.813126Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-05-13T13:01:56.570",
"references": [
{
"source": "2499f714-1537-4658-8207-48ae4bb9eae9",
"tags": [
"Patch",
"Vendor Advisory"
],
"url": "https://curl.se/docs/CVE-2026-6253.html"
},
{
"source": "2499f714-1537-4658-8207-48ae4bb9eae9",
"tags": [
"Vendor Advisory"
],
"url": "https://curl.se/docs/CVE-2026-6253.json"
},
{
"source": "2499f714-1537-4658-8207-48ae4bb9eae9",
"tags": [
"Exploit",
"Issue Tracking",
"Third Party Advisory"
],
"url": "https://hackerone.com/reports/3669637"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Mailing List",
"Patch",
"Third Party Advisory"
],
"url": "http://www.openwall.com/lists/oss-security/2026/04/29/11"
},
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"tags": [
"Exploit",
"Issue Tracking",
"Third Party Advisory"
],
"url": "https://hackerone.com/reports/3669637"
}
],
"sourceIdentifier": "2499f714-1537-4658-8207-48ae4bb9eae9",
"vulnStatus": "Modified",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-522"
}
],
"source": "2499f714-1537-4658-8207-48ae4bb9eae9",
"type": "Secondary"
},
{
"description": [
{
"lang": "en",
"value": "CWE-522"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
}
]
}
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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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