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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

PUBLISHED Reserved 2026-04-13 | Published 2026-05-13 | Updated 2026-05-13 | Assigner curl

Problem types

CWE-522 Insufficiently Protected Credentials

Product status

Default status
unaffected

8.19.0 (semver)
affected

8.18.0 (semver)
affected

8.17.0 (semver)
affected

8.16.0 (semver)
affected

8.15.0 (semver)
affected

8.14.1 (semver)
affected

8.14.0 (semver)
affected

8.13.0 (semver)
affected

8.12.1 (semver)
affected

8.12.0 (semver)
affected

8.11.1 (semver)
affected

8.11.0 (semver)
affected

8.10.1 (semver)
affected

8.10.0 (semver)
affected

8.9.1 (semver)
affected

8.9.0 (semver)
affected

8.8.0 (semver)
affected

8.7.1 (semver)
affected

8.7.0 (semver)
affected

8.6.0 (semver)
affected

8.5.0 (semver)
affected

8.4.0 (semver)
affected

8.3.0 (semver)
affected

8.2.1 (semver)
affected

8.2.0 (semver)
affected

8.1.2 (semver)
affected

8.1.1 (semver)
affected

8.1.0 (semver)
affected

8.0.1 (semver)
affected

8.0.0 (semver)
affected

7.88.1 (semver)
affected

7.88.0 (semver)
affected

7.87.0 (semver)
affected

7.86.0 (semver)
affected

7.85.0 (semver)
affected

7.84.0 (semver)
affected

7.83.1 (semver)
affected

7.83.0 (semver)
affected

7.82.0 (semver)
affected

7.81.0 (semver)
affected

7.80.0 (semver)
affected

7.79.1 (semver)
affected

7.79.0 (semver)
affected

7.78.0 (semver)
affected

7.77.0 (semver)
affected

7.76.1 (semver)
affected

7.76.0 (semver)
affected

7.75.0 (semver)
affected

7.74.0 (semver)
affected

7.73.0 (semver)
affected

7.72.0 (semver)
affected

7.71.1 (semver)
affected

7.71.0 (semver)
affected

7.70.0 (semver)
affected

7.69.1 (semver)
affected

7.69.0 (semver)
affected

7.68.0 (semver)
affected

7.67.0 (semver)
affected

7.66.0 (semver)
affected

7.65.3 (semver)
affected

7.65.2 (semver)
affected

7.65.1 (semver)
affected

7.65.0 (semver)
affected

7.64.1 (semver)
affected

7.64.0 (semver)
affected

7.63.0 (semver)
affected

7.62.0 (semver)
affected

7.61.1 (semver)
affected

7.61.0 (semver)
affected

7.60.0 (semver)
affected

7.59.0 (semver)
affected

7.58.0 (semver)
affected

7.57.0 (semver)
affected

7.56.1 (semver)
affected

7.56.0 (semver)
affected

7.55.1 (semver)
affected

7.55.0 (semver)
affected

7.54.1 (semver)
affected

7.54.0 (semver)
affected

7.53.1 (semver)
affected

7.53.0 (semver)
affected

7.52.1 (semver)
affected

7.52.0 (semver)
affected

7.51.0 (semver)
affected

7.50.3 (semver)
affected

7.50.2 (semver)
affected

7.50.1 (semver)
affected

7.50.0 (semver)
affected

7.49.1 (semver)
affected

7.49.0 (semver)
affected

7.48.0 (semver)
affected

7.47.1 (semver)
affected

7.47.0 (semver)
affected

7.46.0 (semver)
affected

7.45.0 (semver)
affected

7.44.0 (semver)
affected

7.43.0 (semver)
affected

7.42.1 (semver)
affected

7.42.0 (semver)
affected

7.41.0 (semver)
affected

7.40.0 (semver)
affected

7.39.0 (semver)
affected

7.38.0 (semver)
affected

7.37.1 (semver)
affected

7.37.0 (semver)
affected

7.36.0 (semver)
affected

7.35.0 (semver)
affected

7.34.0 (semver)
affected

7.33.0 (semver)
affected

7.32.0 (semver)
affected

7.31.0 (semver)
affected

7.30.0 (semver)
affected

7.29.0 (semver)
affected

7.28.1 (semver)
affected

7.28.0 (semver)
affected

7.27.0 (semver)
affected

7.26.0 (semver)
affected

7.25.0 (semver)
affected

7.24.0 (semver)
affected

7.23.1 (semver)
affected

7.23.0 (semver)
affected

7.22.0 (semver)
affected

7.21.7 (semver)
affected

7.21.6 (semver)
affected

7.21.5 (semver)
affected

7.21.4 (semver)
affected

7.21.3 (semver)
affected

7.21.2 (semver)
affected

7.21.1 (semver)
affected

7.21.0 (semver)
affected

7.20.1 (semver)
affected

7.20.0 (semver)
affected

7.19.7 (semver)
affected

7.19.6 (semver)
affected

7.19.5 (semver)
affected

7.19.4 (semver)
affected

7.19.3 (semver)
affected

7.19.2 (semver)
affected

7.19.1 (semver)
affected

7.19.0 (semver)
affected

7.18.2 (semver)
affected

7.18.1 (semver)
affected

7.18.0 (semver)
affected

7.17.1 (semver)
affected

7.17.0 (semver)
affected

7.16.4 (semver)
affected

7.16.3 (semver)
affected

7.16.2 (semver)
affected

7.16.1 (semver)
affected

7.16.0 (semver)
affected

7.15.5 (semver)
affected

7.15.4 (semver)
affected

7.15.3 (semver)
affected

7.15.2 (semver)
affected

7.15.1 (semver)
affected

7.15.0 (semver)
affected

7.14.1 (semver)
affected

Credits

Dwij Mehta (O2 Lab finder

Texas A&M University) finder

Daniel Stenberg remediation developer

References

www.openwall.com/lists/oss-security/2026/04/29/11

hackerone.com/reports/3669637 exploit

curl.se/docs/CVE-2026-6253.json (json)

curl.se/docs/CVE-2026-6253.html (www)

hackerone.com/reports/3669637 (issue)

cve.org (CVE-2026-6253)

nvd.nist.gov (CVE-2026-6253)

Download JSON