Description
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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| curl | curl | 8.18.0 – < 8.20.1, 8.20.0, 8.19.0, 8.18.0 | 8.20.1 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | curl | 8.21.0~rc2-1 | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Hardened Images 1 | curl +3 | 8.21.0-0.1.hum1 | RHSA-2026:29017 |
| Red Hat Hardened Images 1 | rust +18 | 1.96.1-1.hum1 | RHSA-2026:34975 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | curl | 8.22.0-150700.7.33.1 | SUSE-SU-2026:5068-1 |
| SLES 15 SP6 | curl | 8.22.0-150600.4.58.1 | SUSE-SU-2026:5069-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 15 SP6 | curl | 8.22.0-150600.4.58.1 | SUSE-SU-2026:5069-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | curl | 8.21.0-1.1 | openSUSE-SU-2026:11230-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | curl | 8.21.0-r0 | — |
| Alpine v3.23 | curl | 8.22.0-r0 | — |
Advisories 6
- WID-SEC-2026-2052 cURL: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 12, 2026
- SUSE-SU-2026:5069-1 Security update for curl SUSE / openSUSE Security Updates · Nov 3, 2026
- SUSE-SU-2026:5068-1 Security update for curl SUSE / openSUSE Security Updates · Nov 3, 2026
- RHSA-2026:34975 Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update Red Hat Security Advisories (RHSA) · Oct 17, 2026
- RHSA-2026:29017 Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update Red Hat Security Advisories (RHSA) · Oct 17, 2026
- openSUSE-SU-2026:11230-1 curl-8.21.0-1.1 on GA media SUSE / openSUSE Security Updates · Jul 10, 2026