-J no-clobber guarantee bypassed with 103 early hints
When invoked with `--remote-header-name` (`-J`), curl fails to preserve its
documented anti-clobbering protection if an intermediate 103 Early Hints
response precedes the final HTTP response, or if an `ETag` header is processed
before `Content-Disposition` under `--etag-save`. This flaw allows an HTTP(S)
server to overwrite an existing local file specified in the
`Content-Disposition` header despite the presence of the `-J` non-overwrite
constraint.
libcurl's TFTP state machine fails to validate state transitions against the
requested transfer direction, accepting opening server responses for both
reads and writes interchangeably. A malicious TFTP server can respond to a
download request in a way that forces the client into transmit mode, prompting
libcurl to consume and transmit data from the handle's persistent
`CURLOPT_READDATA` pointer - including data remaining from unrelated prior
operations, such as an HTTP POST request executed on a reused handle.
When an FTP wildcard `LIST` operation fails, libcurl omits the restoration
path meant for successful listings, leaving the write callback set to the
internal listing parser and the write callback data pointing directly to the
easy handle. Subsequent reuse of this handle triggers an immediate crash, and
cloning it via `curl_easy_duphandle()` copies this corrupted state into the
duplicate. If the original handle is subsequently freed, executing a transfer
on the cloned handle causes a heap use-after-free read against the dangling
handle reference; alternatively, reusing the original or cloned handle while
changing only `CURLOPT_WRITEDATA` (and
IMAP APPEND plus CRLF conversion command injection
Enabling `CURLOPT_CRLF` causes curl to advertise the raw input byte count in
the `IMAP APPEND {N}` literal while transmitting line-ending expanded data.
The server reads only $N$ bytes for the payload, causing the remaining
overflow bytes to be interpreted and executed as pipelined IMAP commands
within the authenticated session.
An HTTP proxy can trick libcurl into sending the origin's credentials (Basic
password, or a Negotiate/Kerberos ticket) to the proxy itself, by answering
the `CONNECT` tunnel request with 401 `WWW-Authenticate:` instead of the
expected 407 `Proxy-Authenticate:`.
When `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 established without a presented server certificate. Bypassing the
pinning check under these disabled-verification conditions allows
unauthenticated connections to succeed when they should be rejected.
A flaw in libcurl's handling of HTTP/2 Server Push streams, when the parent
handle is set to share connections with other handles, can lead to
use-after-free in the cleanup process.
High · CVSS 7.5EPSS 0.4%Public exploitNo fix published
incomplete mTLS config matching in conn reuse
libcurl would reuse a previously created connection even when some mTLS config
related option had been changed that should have prohibited reuse.
libcurl keeps previously used connections in a connection pool for subsequent
transfers to reuse if one of them matches the setup. However, some TLS
settings related to client certificates were left out from the configuration
match checks, making them match too easily. In particular options related to
the private key.
When reusing a libcurl handle for sequential transfers driven by
environment-variable proxy configuration, libcurl fails to clear the proxy
authentication state between requests. Specifically, if the initial transfer
authenticates against `proxyA` using Digest auth, a subsequent transfer routed
through `proxyB` erroneously leaks the `Proxy-Authorization:` header intended
solely for `proxyA`.
A flaw in curl’s cookie parsing logic allows a malicious HTTP server to set
"super cookies" that bypass the Public Suffix List check. This enables an
attacker-controlled origin to inject cookies that curl subsequently scopes and
transmits to unrelated third-party domains.
A vulnerability exists where a new transfer that uses STARTTLS to upgrade the
connection might reuse an existing live connection even though the TLS
configuration mismatches so it should not.
Successfully using libcurl to do a transfer to a specific HTTP origin
(`hostA`) with **Digest** authentication and then changing the origin to a
different one (`hostB`) for a second transfer, reusing the same handle, makes
libcurl wrongly pass on the `Authorization:` header field meant for `hostA`,
to `hostB`.
netrc credential leak with reused proxy connection
When 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.
curl might erroneously pass on credentials for a first proxy to a second
proxy.
This can happen when the following conditions are true:
1. curl is setup to use specific different proxies for different URL schemes
2. the first proxy needs credentials
3. the second proxy uses no credentials
4. while using the first proxy (using say `http://`), curl is asked to follow
a redirect to a URL using another scheme (say `https://`), accessed using a
second, different, proxy
libcurl might in some circumstances reuse the wrong connection for SMB(S)
transfers.
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 network transfer operation that was requested by an
application could wrongfully reuse an existing SMB connection to the same
server that was using a different "share" than the new subsequent transfer
should.
This could in unlucky situations lead to the download of the wrong file or the
upload of a file to the wrong place. When this happ
A vulnerability exists where a connection requiring TLS incorrectly reuses an
existing unencrypted connection from the same connection pool. If an initial
transfer is made in clear-text (via IMAP, SMTP, or POP3), a subsequent request
to that same host bypasses the TLS requirement and instead transmit data
unencrypted.
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.
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.
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.
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.