CVE-2026-9546

EUVD-2026-41494
A vulnerability in libcurl caused the HTTP `Referer:` header to persist even
when explicitly cleared. While the documentation states that passing NULL to
`CURLOPT_REFERER` suppresses the header, the option failed to clear the
internal state. As a result, the previous referrer string was erroneously
reused and sent in subsequent requests, potentially leaking sensitive
information to unintended servers.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
curlCNA
7.5 HIGH
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Base Score
CVSS 3.x
EPSS Score
Percentile: 49.38%
Affected Products (NVD)
VendorProductVersion
haxxcurl
8.18.0 ≤
𝑥
< 8.21.0
𝑥
= Vulnerable software versions
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources.
VendorProductVersionSource
curlcurl
8.18.0 ≤
𝑥
< 8.20.1
CNA
curlcurl
8.20.0
CNA
curlcurl
8.19.0
CNA
curlcurl
8.18.0
CNA
Debian logo
Debian Releases
Debian Product
Codename
curl
bookworm
7.88.1-10+deb12u15
fixed
bookworm (security)
7.88.1-10+deb12u5
fixed
bullseye
not-affected
forky
8.22.0-1
fixed
sid
8.23.0~rc2-1
fixed
trixie
8.14.1-2+deb13u5
fixed
Ubuntu logo
Ubuntu Releases
Ubuntu Product
Codename
curl
bionic
not-affected
focal
not-affected
jammy
not-affected
noble
not-affected
questing
not-affected
resolute
not-affected
trusty
not-affected
xenial
not-affected
Common Weakness Enumeration
References
https://curl.se/docs/CVE-2026-9546.html
https://curl.se/docs/CVE-2026-9546.json
https://hackerone.com/reports/3754343
https://hackerone.com/reports/3754343