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CVE-2026-6253

proxy credentials leak over redirect-to proxy

Published: May 13, 2026Updated: May 14, 2026 Sources: CVE List NVDCWE-522
NVD MITRE
5.9CVSSMEDIUM
EPSS Score
0.5%
Top 60.3%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
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Weaknesses

CWE-522

Affected Products

curlhaxxOSS Libraries
curlcurl
Library
OSS Libraries / generic-library
haxxoss-projectSEOSS Librariesaka haxx.se
curloss-projectUSOSS Librariesaka libcurl, wcurl

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Official Patch Available

MITRE ATT&CK

2 techniques
Credential Access
View detailed technique mapping

References

https://curl.se/docs/CVE-2026-6253.html
curl.se
https://curl.se/docs/CVE-2026-6253.json
curl.se
https://hackerone.com/reports/3669637
hackerone.com
and 1 more references View all →

Timeline

Published
May 13, 2026
Last Updated
May 14, 2026

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