proxy credentials leak over redirect-to proxy_CVE-2026-6253

5.9 / 10

MEDIUM

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

Description

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

Basic Information

ID CVE-2026-6253

Source curl

Published May 13, 2026 at 08:28

Modified May 13, 2026 at 17:42

Affected Product

Vendor curl

Product curl

Version 8.19.0

Affected Versions curl curl 8.19.0
curl curl 8.18.0
curl curl 8.17.0
curl curl 8.16.0
curl curl 8.15.0
curl curl 8.14.1
curl curl 8.14.0
curl curl 8.13.0
curl curl 8.12.1
curl curl 8.12.0
curl curl 8.11.1
curl curl 8.11.0
curl curl 8.10.1
curl curl 8.10.0
curl curl 8.9.1
curl curl 8.9.0
curl curl 8.8.0
curl curl 8.7.1
curl curl 8.7.0
curl curl 8.6.0
curl curl 8.5.0
curl curl 8.4.0
curl curl 8.3.0
curl curl 8.2.1
curl curl 8.2.0
curl curl 8.1.2
curl curl 8.1.1
curl curl 8.1.0
curl curl 8.0.1
curl curl 8.0.0
curl curl 7.88.1
curl curl 7.88.0
curl curl 7.87.0
curl curl 7.86.0
curl curl 7.85.0
curl curl 7.84.0
curl curl 7.83.1
curl curl 7.83.0
curl curl 7.82.0
curl curl 7.81.0
curl curl 7.80.0
curl curl 7.79.1
curl curl 7.79.0
curl curl 7.78.0
curl curl 7.77.0
curl curl 7.76.1
curl curl 7.76.0
curl curl 7.75.0
curl curl 7.74.0
curl curl 7.73.0
curl curl 7.72.0
curl curl 7.71.1
curl curl 7.71.0
curl curl 7.70.0
curl curl 7.69.1
curl curl 7.69.0
curl curl 7.68.0
curl curl 7.67.0
curl curl 7.66.0
curl curl 7.65.3
curl curl 7.65.2
curl curl 7.65.1
curl curl 7.65.0
curl curl 7.64.1
curl curl 7.64.0
curl curl 7.63.0
curl curl 7.62.0
curl curl 7.61.1
curl curl 7.61.0
curl curl 7.60.0
curl curl 7.59.0
curl curl 7.58.0
curl curl 7.57.0
curl curl 7.56.1
curl curl 7.56.0
curl curl 7.55.1
curl curl 7.55.0
curl curl 7.54.1
curl curl 7.54.0
curl curl 7.53.1
curl curl 7.53.0
curl curl 7.52.1
curl curl 7.52.0
curl curl 7.51.0
curl curl 7.50.3
curl curl 7.50.2
curl curl 7.50.1
curl curl 7.50.0
curl curl 7.49.1
curl curl 7.49.0
curl curl 7.48.0
curl curl 7.47.1
curl curl 7.47.0
curl curl 7.46.0
curl curl 7.45.0
curl curl 7.44.0
curl curl 7.43.0
curl curl 7.42.1
curl curl 7.42.0
curl curl 7.41.0
curl curl 7.40.0
curl curl 7.39.0
curl curl 7.38.0
curl curl 7.37.1
curl curl 7.37.0
curl curl 7.36.0
curl curl 7.35.0
curl curl 7.34.0
curl curl 7.33.0
curl curl 7.32.0
curl curl 7.31.0
curl curl 7.30.0
curl curl 7.29.0
curl curl 7.28.1
curl curl 7.28.0
curl curl 7.27.0
curl curl 7.26.0
curl curl 7.25.0
curl curl 7.24.0
curl curl 7.23.1
curl curl 7.23.0
curl curl 7.22.0
curl curl 7.21.7
curl curl 7.21.6
curl curl 7.21.5
curl curl 7.21.4
curl curl 7.21.3
curl curl 7.21.2
curl curl 7.21.1
curl curl 7.21.0
curl curl 7.20.1
curl curl 7.20.0
curl curl 7.19.7
curl curl 7.19.6
curl curl 7.19.5
curl curl 7.19.4
curl curl 7.19.3
curl curl 7.19.2
curl curl 7.19.1
curl curl 7.19.0
curl curl 7.18.2
curl curl 7.18.1
curl curl 7.18.0
curl curl 7.17.1
curl curl 7.17.0
curl curl 7.16.4
curl curl 7.16.3
curl curl 7.16.2
curl curl 7.16.1
curl curl 7.16.0
curl curl 7.15.5
curl curl 7.15.4
curl curl 7.15.3
curl curl 7.15.2
curl curl 7.15.1
curl curl 7.15.0
curl curl 7.14.1

References

{
    "lastseen": "",
    "description": "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",
    "published": "2026-05-13T08:28:03.004Z",
    "modified": "2026-05-13T17:42:40.102Z",
    "type": "cve",
    "title": "proxy credentials leak over redirect-to proxy",
    "source": "curl",
    "references": "https://curl.se/docs/CVE-2026-6253.json\nhttps://curl.se/docs/CVE-2026-6253.html\nhttps://hackerone.com/reports/3669637",
    "id": "CVE-2026-6253",
    "bulletinFamily": "",
    "cwe": null,
    "cvelist": null,
    "sourceData": "curl curl 8.19.0\ncurl curl 8.18.0\ncurl curl 8.17.0\ncurl curl 8.16.0\ncurl curl 8.15.0\ncurl curl 8.14.1\ncurl curl 8.14.0\ncurl curl 8.13.0\ncurl curl 8.12.1\ncurl curl 8.12.0\ncurl curl 8.11.1\ncurl curl 8.11.0\ncurl curl 8.10.1\ncurl curl 8.10.0\ncurl curl 8.9.1\ncurl curl 8.9.0\ncurl curl 8.8.0\ncurl curl 8.7.1\ncurl curl 8.7.0\ncurl curl 8.6.0\ncurl curl 8.5.0\ncurl curl 8.4.0\ncurl curl 8.3.0\ncurl curl 8.2.1\ncurl curl 8.2.0\ncurl curl 8.1.2\ncurl curl 8.1.1\ncurl curl 8.1.0\ncurl curl 8.0.1\ncurl curl 8.0.0\ncurl curl 7.88.1\ncurl curl 7.88.0\ncurl curl 7.87.0\ncurl curl 7.86.0\ncurl curl 7.85.0\ncurl curl 7.84.0\ncurl curl 7.83.1\ncurl curl 7.83.0\ncurl curl 7.82.0\ncurl curl 7.81.0\ncurl curl 7.80.0\ncurl curl 7.79.1\ncurl curl 7.79.0\ncurl curl 7.78.0\ncurl curl 7.77.0\ncurl curl 7.76.1\ncurl curl 7.76.0\ncurl curl 7.75.0\ncurl curl 7.74.0\ncurl curl 7.73.0\ncurl curl 7.72.0\ncurl curl 7.71.1\ncurl curl 7.71.0\ncurl curl 7.70.0\ncurl curl 7.69.1\ncurl curl 7.69.0\ncurl curl 7.68.0\ncurl curl 7.67.0\ncurl curl 7.66.0\ncurl curl 7.65.3\ncurl curl 7.65.2\ncurl curl 7.65.1\ncurl curl 7.65.0\ncurl curl 7.64.1\ncurl curl 7.64.0\ncurl curl 7.63.0\ncurl curl 7.62.0\ncurl curl 7.61.1\ncurl curl 7.61.0\ncurl curl 7.60.0\ncurl curl 7.59.0\ncurl curl 7.58.0\ncurl curl 7.57.0\ncurl curl 7.56.1\ncurl curl 7.56.0\ncurl curl 7.55.1\ncurl curl 7.55.0\ncurl curl 7.54.1\ncurl curl 7.54.0\ncurl curl 7.53.1\ncurl curl 7.53.0\ncurl curl 7.52.1\ncurl curl 7.52.0\ncurl curl 7.51.0\ncurl curl 7.50.3\ncurl curl 7.50.2\ncurl curl 7.50.1\ncurl curl 7.50.0\ncurl curl 7.49.1\ncurl curl 7.49.0\ncurl curl 7.48.0\ncurl curl 7.47.1\ncurl curl 7.47.0\ncurl curl 7.46.0\ncurl curl 7.45.0\ncurl curl 7.44.0\ncurl curl 7.43.0\ncurl curl 7.42.1\ncurl curl 7.42.0\ncurl curl 7.41.0\ncurl curl 7.40.0\ncurl curl 7.39.0\ncurl curl 7.38.0\ncurl curl 7.37.1\ncurl curl 7.37.0\ncurl curl 7.36.0\ncurl curl 7.35.0\ncurl curl 7.34.0\ncurl curl 7.33.0\ncurl curl 7.32.0\ncurl curl 7.31.0\ncurl curl 7.30.0\ncurl curl 7.29.0\ncurl curl 7.28.1\ncurl curl 7.28.0\ncurl curl 7.27.0\ncurl curl 7.26.0\ncurl curl 7.25.0\ncurl curl 7.24.0\ncurl curl 7.23.1\ncurl curl 7.23.0\ncurl curl 7.22.0\ncurl curl 7.21.7\ncurl curl 7.21.6\ncurl curl 7.21.5\ncurl curl 7.21.4\ncurl curl 7.21.3\ncurl curl 7.21.2\ncurl curl 7.21.1\ncurl curl 7.21.0\ncurl curl 7.20.1\ncurl curl 7.20.0\ncurl curl 7.19.7\ncurl curl 7.19.6\ncurl curl 7.19.5\ncurl curl 7.19.4\ncurl curl 7.19.3\ncurl curl 7.19.2\ncurl curl 7.19.1\ncurl curl 7.19.0\ncurl curl 7.18.2\ncurl curl 7.18.1\ncurl curl 7.18.0\ncurl curl 7.17.1\ncurl curl 7.17.0\ncurl curl 7.16.4\ncurl curl 7.16.3\ncurl curl 7.16.2\ncurl curl 7.16.1\ncurl curl 7.16.0\ncurl curl 7.15.5\ncurl curl 7.15.4\ncurl curl 7.15.3\ncurl curl 7.15.2\ncurl curl 7.15.1\ncurl curl 7.15.0\ncurl curl 7.14.1",
    "sourceHref": "",
    "cvss": {
        "score": 5.9,
        "severity": "MEDIUM",
        "vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "curl",
    "version": "8.19.0",
    "vendor": "curl",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}

Description

Basic Information

Affected Product

References

💭 Join the Security Discussion ❌ Cancel Reply