When doing SSH-based transfers using either SCP or SFTP, and setting the
known_hosts file, libcurl could still mistakenly accept connecting to hosts
*not present* in the specified file if they were added as recognized in the
libssh *global* known_hosts file.
CVSS Score
5.3
EPSS Score
0.0
Published
2026-01-08
When doing SSH-based transfers using either SCP or SFTP, and asked to do
public key authentication, curl would wrongly still ask and authenticate using
a locally running SSH agent.
CVSS Score
3.1
EPSS Score
0.0
Published
2026-01-08
When an OAuth2 bearer token is used for an HTTP(S) transfer, and that transfer
performs a cross-protocol redirect to a second URL that uses an IMAP, LDAP,
POP3 or SMTP scheme, curl might wrongly pass on the bearer token to the new
target host.
CVSS Score
5.3
EPSS Score
0.0
Published
2026-01-08
When doing multi-threaded LDAPS transfers (LDAP over TLS) with libcurl,
changing TLS options in one thread would inadvertently change them globally
and therefore possibly also affect other concurrently setup transfers.
Disabling certificate verification for a specific transfer could
unintentionally disable the feature for other threads as well.
CVSS Score
6.3
EPSS Score
0.0
Published
2026-01-08
curl's code for managing SSH connections when SFTP was done using the wolfSSH
powered backend was flawed and missed host verification mechanisms.
This prevents curl from detecting MITM attackers and more.
CVSS Score
4.3
EPSS Score
0.0
Published
2025-11-07
When asked to use a `.netrc` file for credentials **and** to follow HTTP
redirects, curl could leak the password used for the first host to the
followed-to host under certain circumstances.
This flaw only manifests itself if the netrc file has a `default` entry that
omits both login and password. A rare circumstance.
CVSS Score
3.4
EPSS Score
0.002
Published
2025-02-05
When libcurl is asked to perform automatic gzip decompression of
content-encoded HTTP responses with the `CURLOPT_ACCEPT_ENCODING` option,
**using zlib 1.2.0.3 or older**, an attacker-controlled integer overflow would
make libcurl perform a buffer overflow.
CVSS Score
7.3
EPSS Score
0.009
Published
2025-02-05
When asked to both use a `.netrc` file for credentials and to follow HTTP
redirects, curl could leak the password used for the first host to the
followed-to host under certain circumstances.
This flaw only manifests itself if the netrc file has an entry that matches
the redirect target hostname but the entry either omits just the password or
omits both login and password.
CVSS Score
3.4
EPSS Score
0.009
Published
2024-12-11
When curl is asked to use HSTS, the expiry time for a subdomain might
overwrite a parent domain's cache entry, making it end sooner or later than
otherwise intended.
This affects curl using applications that enable HSTS and use URLs with the
insecure `HTTP://` scheme and perform transfers with hosts like
`x.example.com` as well as `example.com` where the first host is a subdomain
of the second host.
(The HSTS cache either needs to have been populated manually or there needs to
have been previous HTTPS accesses done as the cache needs to have entries for
the domains involved to trigger this problem.)
When `x.example.com` responds with `Strict-Transport-Security:` headers, this
bug can make the subdomain's expiry timeout *bleed over* and get set for the
parent domain `example.com` in curl's HSTS cache.
The result of a triggered bug is that HTTP accesses to `example.com` get
converted to HTTPS for a different period of time than what was asked for by
the origin server. If `example.com` for example stops supporting HTTPS at its
expiry time, curl might then fail to access `http://example.com` until the
(wrongly set) timeout expires. This bug can also expire the parent's entry
*earlier*, thus making curl inadvertently switch back to insecure HTTP earlier
than otherwise intended.
CVSS Score
6.5
EPSS Score
0.006
Published
2024-11-06
When curl is told to use the Certificate Status Request TLS extension, often referred to as OCSP stapling, to verify that the server certificate is valid, it might fail to detect some OCSP problems and instead wrongly consider the response as fine. If the returned status reports another error than 'revoked' (like for example 'unauthorized') it is not treated as a bad certficate.
CVSS Score
6.5
EPSS Score
0.006
Published
2024-09-11
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