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

No CVSS v4.0

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00016.

Exploitation poc

Automatable no

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

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

No data.

No data.

OpenCVE Enrichment is a feature of OpenCVE that uses AI to automatically link vendors and products to CVEs. Learn more on GitHub.

Vendors Products
Curl Subscribe
Curl Subscribe

Project Subscriptions

Vendors Products
Curl Subscribe
Curl Subscribe
Advisories
Source ID Title
Ubuntu USN Ubuntu USN USN-8227-1 curl vulnerabilities
Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
http://www.openwall.com/lists/oss-security/2026/04/29/11 cve-icon
https://curl.se/docs/CVE-2026-6253.html cve-icon cve-icon cve-icon
https://curl.se/docs/CVE-2026-6253.json cve-icon cve-icon
https://hackerone.com/reports/3669637 cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-6253 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-6253 cve-icon
History

Wed, 13 May 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N'}

 ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Wed, 13 May 2026 15:30:00 +0000

Type Values Removed Values Added
References

Wed, 13 May 2026 09:15:00 +0000

Type Values Removed Values Added
Description A flaw was found in curl. When curl is configured to use distinct proxies for different URL schemes, a redirect from a URL using an authenticated proxy to one using an unauthenticated proxy can inadvertently expose the initial proxy's credentials. This improper credential management (CWE-522) may allow an attacker to gain unauthorized access or information by intercepting these disclosed credentials. 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
Title curl: curl: Proxy credential disclosure via redirects to unauthenticated proxies proxy credentials leak over redirect-to proxy
References

Fri, 01 May 2026 01:45:00 +0000

Type Values Removed Values Added
First Time appeared Curl
Curl curl
Vendors & Products Curl
Curl curl

Fri, 01 May 2026 00:15:00 +0000

Type Values Removed Values Added
Description A flaw was found in curl. When curl is configured to use distinct proxies for different URL schemes, a redirect from a URL using an authenticated proxy to one using an unauthenticated proxy can inadvertently expose the initial proxy's credentials. This improper credential management (CWE-522) may allow an attacker to gain unauthorized access or information by intercepting these disclosed credentials.
Title curl: curl: Proxy credential disclosure via redirects to unauthenticated proxies
Weaknesses CWE-201
References
Metrics threat_severity

None

 cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N'}

threat_severity

Moderate

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: curl

Published:

Updated: 2026-05-13T17:42:40.102Z

Reserved: 2026-04-13T20:11:11.991Z

Link: CVE-2026-6253

cve-icon Vulnrichment

Updated: 2026-05-13T09:05:31.000Z

cve-icon NVD

Status : Undergoing Analysis

Published: 2026-05-13T13:01:56.570

Modified: 2026-05-13T18:16:20.090

Link: CVE-2026-6253

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-04-29T00:00:00Z

Links: CVE-2026-6253 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-05-13T10:30:16Z

Weaknesses