Vulnerability Report

CVE-2026-6253

Title: Proxy credential leakage

Information Disclosure

Proof Of Concept

No public PoC currently indexed for CVE-2026-6253.

CWE Category NVD-CWE-noinfo
Published Date May 13, 2026
Modified Date May 14, 2026
Exploit Status Not Found
Score 5.9 CVSS v
Exploit Probability (EPSS)
0.03%

Vulnerability Summary

CVE-2026-6253: 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

Impacted Vendors

D
daniel_stenberg 1
H
haxx 1

Reference Links

https://curl.se/docs/CVE-2026-6253.html https://curl.se/docs/CVE-2026-6253.json https://hackerone.com/reports/3669637 http://www.openwall.com/lists/oss-security/2026/04/29/11
CVSS v3.1
Source Entity 134c704f-9b21-4f2e-91b3-4a467353bcc0
Severity MEDIUM
5.9
Attack Vector
NETWORK
Complexity
HIGH
Privileges
N/A
Interaction
NONE
Confidentiality
N/A
Integrity
N/A
Availability
N/A
Scope
UNCHANGED
RAW VECTOR CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Associated Attack Patterns (CAPEC)

Total: Patterns

CVE-2026-6253 Exploits & PoCs (Proof Of Concept)

No public PoCs found in our database for this CVE.

MODIFIED

Vulnerability data updated via NVD.

MODIFIED

Vulnerability data updated via NVD.

MODIFIED

Vulnerability data updated via NVD.

Attack Vector Matrix

Access Vector NETWORK
Complexity HIGH
Privileges N/A
Interaction NONE
CVSS Vector String CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected Stack

No specific products linked.