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CVE-2026-11352

QUIC zero-length UDP datagrams busy-loop

An issue in curl’s QUIC UDP receive function allows a malicious HTTP/3 server to trigger a remote denial of service against a curl or libcurl client. Because the helper function discards zero-length UDP datagrams before counting them toward the per-call packet budget, a connected QUIC peer can continuously stream empty datagrams to indefinitely stall the client.

CVSS 3.1 · 7.5 High EPSS 1.0% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2026-11586

WS Auto-PONG memory exhaustion

By default, curl automatically responds to WebSocket PING frames. Because curl lacks an upper bound on memory allocation for unacknowledged frames, a malicious server can exhaust all available memory by flooding curl with rapid, sequential PING messages.

CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2026-8927

env-set cross-proxy Digest auth state leak

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`.

CVSS 3.1 · 9.1 Critical EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2026-9080

UAF after pause in socket callback

Calling `curl_easy_pause()` within the event-based `CURLMOPT_SOCKETFUNCTION` callback triggers a use-after-free vulnerability, where libcurl attempts to store a flag using a dangling struct pointer immediately after that pointer's memory has been freed.

CVSS 3.1 · 7.3 High EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2026-8286

wrong STARTTLS connection reuse

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.

CVSS 3.1 · 8.1 High EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2026-9079

stale proxy password leak

libcurl had a flaw that when instructed to clear proxy authentication credentials which made it not do so, leaving the old credentials around to get used for subsequent transfers that should not know nor use them.

CVSS 3.1 · 9.8 Critical EPSS 1.1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2026-7168

cross-proxy Digest auth state leak

Successfully using libcurl to do a transfer over a specific HTTP proxy (`proxyA`) with **Digest** authentication and then changing the proxy host to a second one (`proxyB`) for a second transfer, reusing the same handle, makes libcurl wrongly pass on the `Proxy-Authorization:` header field meant for `proxyA`, to `proxyB`.

CVSS 3.1 · 5.3 Medium EPSS < 1% KEV · Not listed
Vendors
Curl Haxx Redhat
Products
Curl Curl Hummingbird
CVE-2026-3784

wrong proxy connection reuse with credentials

curl 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.

CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2025-10966

missing SFTP host verification with wolfSSH

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 3.1 · 4.3 Medium EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2026-7009

OCSP stapling bypass with Apple SecTrust

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 fails to detect OCSP problems and instead wrongly consider the response as fine.

CVSS 3.1 · 5.3 Medium EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2026-6276

stale custom cookie host causes cookie leak

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.

CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Libcurl Curl
CVE-2026-4873

connection reuse ignores TLS requirement

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.

CVSS 3.1 · 5.9 Medium EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2026-6253

proxy credentials leak over redirect-to proxy

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

CVSS 3.1 · 5.9 Medium EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2009-0037

curl: local file access via unsafe redirects

The redirect implementation in curl and libcurl 5.11 through 7.19.3, when CURLOPT_FOLLOWLOCATION is enabled, accepts arbitrary Location values, which might allow remote HTTP servers to (1) trigger arbitrary requests to intranet servers, (2) read or overwrite arbitrary files via a redirect to a file: URL, or (3) execute arbitrary commands via a redirect to an scp: URL.

CVSS 2.0 · 6.8 Medium EPSS 9.0% KEV · Not listed
Vendors
Curl Redhat
Products
Curl Libcurl Enterprise Linux
CVE-2009-2417

curl: incorrect verification of SSL certificate with NUL in name

lib/ssluse.c in cURL and libcurl 7.4 through 7.19.5, when OpenSSL is used, does not properly handle a '\0' character in a domain name in the subject's Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority, a related issue to CVE-2009-2408.

CVSS 2.0 · 7.5 High EPSS 3.5% KEV · Not listed
Vendors
Curl Libcurl Redhat
Products
Libcurl Libcurl Enterprise Linux
CVE-2005-3185

security flaw

Stack-based buffer overflow in the ntlm_output function in http-ntlm.c for (1) wget 1.10, (2) curl 7.13.2, and (3) libcurl 7.13.2, and other products that use libcurl, when NTLM authentication is enabled, allows remote servers to execute arbitrary code via a long NTLM username.

CVSS 2.0 · 7.5 High EPSS 5.2% KEV · Not listed
Vendors
Curl Libcurl Redhat and 1 more
Products
Curl Libcurl Enterprise Linux and 1 more
CVE-2026-3783

token leak with redirect and netrc

When an OAuth2 bearer token is used for an HTTP(S) transfer, and that transfer performs a redirect to a second URL, curl could leak that token to the second hostname under some circumstances. If the hostname that the first request is redirected to has information in the used .netrc file, with either of the `machine` or `default` keywords, curl would pass on the bearer token set for the first host also to the second one.

CVSS 3.1 · 5.3 Medium EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2026-3805

use after free in SMB connection reuse

When doing a second SMB request to the same host again, curl would wrongly use a data pointer pointing into already freed memory.

CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2025-11563

wcurl path traversal with percent-encoded slashes

URLs containing percent-encoded slashes (`/` or `\`) can trick wcurl into saving the output file outside of the current directory without the user explicitly asking for it. This flaw only affects the wcurl command line tool.

CVSS 3.1 · 4.6 Medium EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Wcurl Curl
CVE-2025-15079

libssh global known_hosts override

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 3.1 · 5.3 Medium EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl