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Description

Using libcurl, when a custom `Host:` header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom `Host:` header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them.

PUBLISHED Reserved 2026-04-14 | Published 2026-05-13 | Updated 2026-05-13 | Assigner curl

Problem types

CWE-346 Origin Validation Error

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

Credits

Muhamad Arga Reksapati finder

Daniel Stenberg remediation developer

References

www.openwall.com/lists/oss-security/2026/04/29/13

hackerone.com/reports/3671818 exploit

curl.se/docs/CVE-2026-6276.json (json)

curl.se/docs/CVE-2026-6276.html (www)

hackerone.com/reports/3671818 (issue)

cve.org (CVE-2026-6276)

nvd.nist.gov (CVE-2026-6276)

Download JSON