CVE-2026-6276High· 7.5▾ MidnightPoC availableUsing 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…
▾ Midnight zone — Critical, or high with PoC / in-the-wild
impact 41.3 · likelihood 0.1 · exploitation 12
A public proof-of-concept already exists for this vulnerability — see Exploit availability below.
Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake.
Exploit-prediction probability, daily snapshots since Sep 15.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
Last analysed / modified upstream
0.3%
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.
curl >= 7.71.0, < 8.20.0Upgrade past the affected range:
curl 8.20.0Connected by shared product, vendor, weakness, or advisory.
CVE-2026-6253Medium· 5.9curl might erroneously pass on credentials for a first proxy to a second proxy. This can happen when the following conditions are true: 1
CVE-2026-6429Medium· 5.3When asked to both use a `.netrc` file for credentials and to follow HTTP redirects, libcurl could leak the password used for the first host to the followed-to host under certain circumstances.
CVE-2026-5545Medium· 6.5libcurl might in some circumstances reuse the wrong connection when asked to do an authenticated HTTP(S) request after a Negotiate-authenticated one, when both use the same host. libcurl features a pool of recent connections so that sub…
CVE-2026-82209High· 8.2When libpsl support is enabled, libcurl fails to enforce the Public Suffix List boundary check when processing a `Set-Cookie` header where the `Domain` attribute explicitly matches an origin host that is itself a public suffix (e.g., `Do…
CVE-2026-80230High· 7.5When `CURLOPT_PINNEDPUBLICKEY` is configured alongside options that disable standard peer verification (`CURLOPT_SSL_VERIFYPEER = 0` and `CURLOPT_SSL_VERIFYHOST = 0`), libcurl fails to enforce public key pinning on connections establishe…
CVE-2026-19931Critical· 9.8A flaw in libcurl makes it wrongly reuse an HTTP connection setup for a given hostname using Negotiate authentication, when the initial request is done using empty credentials