CVE-2026-5545Medium· 6.5▾ Sunlitlibcurl 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…
▾ Sunlit zone — Low / medium · no exploitation signal
impact 35.8 · likelihood 0.1 · exploitation 0
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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
0.4%
libcurl 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 subsequent requests can reuse an existing connection to avoid overhead.
When reusing a connection a range of criteria must be met. Due to a logical error in the code, a request that was issued by an application could wrongfully reuse an existing connection to the same server that was authenticated using different credentials.
An application that first uses Negotiate authentication to a server with
user1:password1 and then does another operation to the same server asking
for any authentication method but for user2:password2 (while the previous
connection is still alive) - the second request gets confused and wrongly
reuses the same connection and sends the new request over that connection
thinking it uses a mix of user1's and user2's credentials when it is in fact
still using the connection authenticated for user1...
curl >= 7.10.6, < 8.20.0Upgrade past the affected range:
curl 8.20.0Connected by shared product, vendor, weakness, or advisory.
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
CVE-2026-8458Medium· 6.5libcurl might in some circumstances reuse the wrong connection when asked to do Negotiate-authenticated ones, even when they are set to use different "services". libcurl features a pool of recent connections so that subsequent requests …
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-2026-6276High· 7.5Using 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…
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-2026-3784Medium· 6.5curl would wrongly reuse an existing HTTP proxy connection doing CONNECT to a server, even if the new request uses different credentials for the HTTP proxy. The proper behavior is to create or use a separate connection.