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© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2026-6253

27
FAUCET Score

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

First published: May 13, 2026Last modified: May 13, 2026

Impacted Technologies

VendorProductVersion(s)CPE
>= 7.14.1, < 8.20.0CPE matchmatch criteria
cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*
>= 7.14.1, <= 7.14.1CPE match
cpe:2.3:a:curl:curl:*:*:*:*:*:*:*:*
>= 7.15.0, <= 7.15.0CPE match
cpe:2.3:a:curl:curl:*:*:*:*:*:*:*:*
>= 7.15.1, <= 7.15.1CPE match
cpe:2.3:a:curl:curl:*:*:*:*:*:*:*:*
>= 7.15.2, <= 7.15.2CPE match
cpe:2.3:a:curl:curl:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.9MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.2
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.72%
Probability of exploitation in next 30 days
EPSS Percentile
50.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0072 is in the 10th percentile among its peer group of 19,958 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.2 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (8)

microsoftpatch availablevia msrc
Product: azl3 cmake 3.30.3-13 on Azure Linux 3.0Fixed in: 3.30.3-14
microsoftpatch availablevia msrc
Product: azl3 curl 8.11.1-7 on Azure Linux 3.0Fixed in: 8.11.1-8
microsoftpatch availablevia msrc
Product: 21119-17084Fixed in: 3.30.3-14
microsoftpatch availablevia msrc
Product: 21382-17084Fixed in: 8.11.1-8
ubuntupatch availablevia ubuntu_usn
Product: curl (questing)Fixed in: 8.14.1-2ubuntu1.3
ubuntupatch availablevia ubuntu_usn
Product: curl (resolute)Fixed in: 8.18.0-1ubuntu2.1
ubuntupatch availablevia ubuntu_usn
Product: curl (jammy)Fixed in: 7.81.0-1ubuntu1.24
ubuntupatch availablevia ubuntu_usn
Product: curl (noble)Fixed in: 8.5.0-2ubuntu10.9

Vendor Advisories (2)

microsoft2026-May/CVE-2026-6253Moderate

proxy credentials leak over redirect-to proxy

May 12, 2026
ubuntuUSN-8227-1

curl vulnerabilities

May 4, 2026

References

curl.se / docs/CVE-2026-6253.html
PatchVendor Advisory
curl.se / docs/CVE-2026-6253.json
Vendor Advisory
hackerone.com / reports/3669637
ExploitIssue TrackingThird Party Advisory
openwall.com / lists/oss-security/2026/04/29/11
Mailing ListPatchThird Party Advisory