Haxx: Security Vulnerabilities
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
1. A cookie is set using the `secure` keyword for `https://target`
2. curl is redirected to or otherwise made to speak with `http://target` (same
hostname, but using clear text HTTP) using the same cookie set
3. The same cookie name is set - but with just a slash as path (`path=\"/\",`).
Since this site is not secure, the cookie *should* just be ignored.
4. A bug in the path comparison logic makes curl read outside a heap buffer
boundary
The bug either causes a crash or it potentially makes the comparison come to
the wrong conclusion and lets the clear-text site override the contents of the
secure cookie, contrary to expectations and depending on the memory contents
immediately following the single-byte allocation that holds the path.
The presumed and correct behavior would be to plainly ignore the second set of
the cookie since it was already set as secure on a secure host so overriding
it on an insecure host should not be okay.
CVSS Score
7.5
EPSS Score
0.0
Published
2025-09-12
curl's websocket code did not update the 32 bit mask pattern for each new
outgoing frame as the specification says. Instead it used a fixed mask that
persisted and was used throughout the entire connection.
A predictable mask pattern allows for a malicious server to induce traffic
between the two communicating parties that could be interpreted by an involved
proxy (configured or transparent) as genuine, real, HTTP traffic with content
and thereby poison its cache. That cached poisoned content could then be
served to all users of that proxy.
CVSS Score
5.3
EPSS Score
0.001
Published
2025-09-12
Due to a mistake in libcurl's WebSocket code, a malicious server can send a
particularly crafted packet which makes libcurl get trapped in an endless
busy-loop.
There is no other way for the application to escape or exit this loop other
than killing the thread/process.
This might be used to DoS libcurl-using application.
CVSS Score
7.5
EPSS Score
0.005
Published
2025-06-07
libcurl accidentally skips the certificate verification for QUIC connections when connecting to a host specified as an IP address in the URL. Therefore, it does not detect impostors or man-in-the-middle attacks.
CVSS Score
6.5
EPSS Score
0.001
Published
2025-05-28
libcurl supports *pinning* of the server certificate public key for HTTPS transfers. Due to an omission, this check is not performed when connecting with QUIC for HTTP/3, when the TLS backend is wolfSSL. Documentation says the option works with wolfSSL, failing to specify that it does not for QUIC and HTTP/3. Since pinning makes the transfer succeed if the pin is fine, users could unwittingly connect to an impostor server without noticing.
CVSS Score
4.8
EPSS Score
0.001
Published
2025-05-28
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
0.003
Published
2025-02-05
libcurl would wrongly close the same eventfd file descriptor twice when taking
down a connection channel after having completed a threaded name resolve.
CVSS Score
7.0
EPSS Score
0.046
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
0.004
Published
2025-02-05