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CVE-2026-80229

OpenSSL provider use-after-free

When performing transfers via libcurl’s multi interface, pooled TLS connections can outlive their originating easy handles. In OpenSSL 3 provider configurations, libcurl attaches an allocated library context to the easy handle's state and passes it to OpenSSL without acquiring an ownership reference; destroying the easy handle prematurely frees this context while the active connection retains a dangling pointer, leading to a heap-use-after-free upon subsequent I/O or post-handshake operations.

CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2026-10536

HTTP/2 stream-dependency tree UAF

A use-after-free vulnerability exists in libcurl when an application configures an HTTP/2 stream-dependency tree via `CURLOPT_STREAM_DEPENDS` or `CURLOPT_STREAM_DEPENDS_E`, subsequently invokes `curl_easy_reset()`, and finally terminates the handle with `curl_easy_cleanup()`. During this final cleanup phase, libcurl attempts to access and modify an internal structure that was already freed during the reset operation.

CVSS 3.1 · 9.8 Critical EPSS < 1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
CVE-2026-11564

Native CA trust persist

libcurl keeps previously used connections in a connection pool for subsequent transfers to reuse if one of them matches the setup. An easy handle that first uses default native CA trust can continue trusting the native platform store after the application switches that same handle to custom CA material for a later transfer.

CVSS 3.1 · 9.1 Critical EPSS < 1% KEV · Not listed
Vendors
Curl Haxx Redhat
Products
Curl Curl Hummingbird
CVE-2026-8925

SASL double-free

The curl logic that works with SASL authentication could end up cleaning up the GSASL context *twice* without clearing the pointer in between, making it `free()` the same pointer twice.

CVSS 3.1 · 9.8 Critical EPSS 1.1% KEV · Not listed
Vendors
Curl Haxx
Products
Curl Curl
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-2023-46219

curl: excessively long file name may lead to unknown HSTS status

When saving HSTS data to an excessively long file name, curl could end up removing all contents, making subsequent requests using that file unaware of the HSTS status they should otherwise use.

CVSS 3.1 · 5.3 Medium EPSS 1.1% KEV · Not listed
Vendors
Fedoraproject Haxx Redhat
Products
Fedora Curl Jboss Core Services
CVE-2023-46218

curl: information disclosure by exploiting a mixed case flaw

This flaw allows a malicious HTTP server to set "super cookies" in curl that are then passed back to more origins than what is otherwise allowed or possible. This allows a site to set cookies that then would get sent to different and unrelated sites and domains. It could do this by exploiting a mixed case flaw in curl's function that verifies a given cookie domain against the Public Suffix List (PSL). For example a cookie could be set with `domain=co.UK` when the URL used a lower case hostname `curl.co.uk`, even though `co.uk` is listed as a PSL domain.

CVSS 3.1 · 6.5 Medium EPSS 1.7% KEV · Not listed
Vendors
Fedoraproject Haxx Redhat
Products
Fedora Curl Enterprise Linux and 4 more
CVE-2017-7407

curl: --write-out out of bounds read

The ourWriteOut function in tool_writeout.c in curl 7.53.1 might allow physically proximate attackers to obtain sensitive information from process memory in opportunistic circumstances by reading a workstation screen during use of a --write-out argument ending in a '%' character, which leads to a heap-based buffer over-read.

CVSS 3.1 · 2.4 Low EPSS < 1% KEV · Not listed
Vendors
Haxx Redhat
Products
Curl Rhel Software Collections