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 happens, the same credentials are used and the server name is the same.

According to the versions of the curl packages installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

    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 happens, the same credentials     are used and the server name is the same.(CVE-2026-5773)

    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.(CVE-2026-6276)

    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.(CVE-2026-3784)

    libcurl can in some circumstances reuse the wrong connection when asked to do     an Negotiate-authenticated HTTP or HTTPS request.

    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 criterion must first be met. Due to a     logical error in the code, a request that was issued by an application could     wrongfully reuse an existing connection to the same server that was     authenticated using different credentials. One underlying reason being that     Negotiate sometimes authenticates *connections* and not *requests*, contrary     to how HTTP is designed to work.

    An application that allows Negotiate authentication to a server (that responds     wanting Negotiate) with `user1:password1` and then does another operation to     the same server also using Negotiate but with `user2:password2` (while the     previous connection is still alive) - the second request wrongly reused the     same connection and since it then sees that the Negotiate negotiation is     already made, it just sends the request over that connection thinking it uses     the user2 credentials when it is in fact still using the connection     authenticated for user1...

    The set of authentication methods to use is set with  `CURLOPT_HTTPAUTH`.

    Applications can disable libcurl's reuse of connections and thus mitigate this     problem, by using one of the following libcurl options to alter how     connections are or are not reused: `CURLOPT_FRESH_CONNECT`,     `CURLOPT_MAXCONNECTS` and `CURLMOPT_MAX_HOST_CONNECTIONS` (if using the     curl_multi API).(CVE-2026-1965)

    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.(CVE-2026-3783)

Tenable has extracted the preceding description block directly from the EulerOS curl security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS / 24.04 LTS / 26.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8525-1 advisory.

    Harry Sintonen discovered that curl incorrectly handled credentials when following HTTP redirects in     conjunction with .netrc files. An attacker could possibly use this issue to obtain sensitive information.
    This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS, and Ubuntu 18.04 LTS. (CVE-2024-11053)

    Hiroki Kurosawa discovered that curl incorrectly handled OCSP stapling responses. A remote attacker could     possibly use this issue to obtain sensitive information. This issue only affected Ubuntu 16.04 LTS and     Ubuntu 18.04 LTS. (CVE-2024-8096)

    Joshua Rogers discovered that curl had a use-after-free vulnerability when resetting and cleaning up     HTTP/2 stream handles. An attacker could possibly use this issue to cause a denial of service or execute     arbitrary code. This issue only affected Ubuntu 24.04 LTS, Ubuntu 25.04, and Ubuntu 25.10.
    (CVE-2026-10536)

    Quac Tran and Ngoc Hieu discovered that curl incorrectly reused connections when switching authentication     methods to the same host. An attacker could possibly use this issue to obtain sensitive information or     perform unauthorized actions. This issue only affected Ubuntu 20.04 LTS. (CVE-2026-5545)

    Osama Hamad discovered that curl incorrectly reused SMB connections when the target share differed between     transfers. An attacker could possibly use this issue to obtain sensitive information. This issue only     affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. (CVE-2026-5773)

    Muhamad Arga Reksapati discovered that curl incorrectly forwarded Digest proxy authentication credentials     to a different proxy host. An attacker could possibly use this issue to obtain sensitive information. This     issue only affected Ubuntu 18.04 LTS and Ubuntu 20.04 LTS. (CVE-2026-7168)

    It was discovered that curl incorrectly skipped SSH host verification options when using schemeless URLs     with --proto-default. An attacker could possibly use this issue to perform machine-in-the-middle attacks.
    This issue only affected Ubuntu 25.04 and Ubuntu 25.10. (CVE-2026-12064)

    It was discovered that curl did not enforce an upper bound on memory allocated for unacknowledged     WebSocket PING frames. A remote attacker could possibly use this issue to cause a denial of service. This     issue only affected Ubuntu 25.10. (CVE-2026-11586)

    It was discovered that curl could stall indefinitely when a malicious HTTP/3 server sent a continuous     stream of empty UDP datagrams. A remote attacker could possibly use this issue to cause a denial of     service. This issue only affected Ubuntu 25.10. (CVE-2026-11352)

    It was discovered that curl could incorrectly continue trusting a native platform CA store after an     application switched the handle to use custom CA material. An attacker could possibly use this issue to     obtain sensitive information. This issue only affected Ubuntu 25.10. (CVE-2026-11564)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

According to the versions of the curl packages installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

    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.(CVE-2026-6276)

    libcurl might in some circumstances reuse the wrong connection when asked to     do an authenticated HTTP(S) request after a Negotiate-authenticated one, when     both use the same host.

    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 request that was issued by an application could     wrongfully reuse an existing connection to the same server that was     authenticated using different credentials.

    An application that first uses Negotiate authentication to a server with     `user1:password1` and then does another operation to the same server asking     for any authentication method but for `user2:password2` (while the previous     connection is still alive) - the second request gets confused and wrongly     reuses the same connection and sends the new request over that connection     thinking it uses a mix of user1's and user2's credentials when it is in fact     still using the connection authenticated for user1...(CVE-2026-5545)

    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(CVE-2026-6253)

    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 happens, the same credentials     are used and the server name is the same.(CVE-2026-5773)

    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.(CVE-2026-4873)

    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.(CVE-2026-6429)

    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`.(CVE-2026-7168)

Tenable has extracted the preceding description block directly from the EulerOS curl security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote SUSE Linux SLES12 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:2703-1 advisory.

    This update for curl fixes the following issues

    - CVE-2026-4873: connection reuse ignores TLS requirement (bsc#1262631).
    - CVE-2026-5545: wrong reuse of HTTP Negotiate connection (bsc#1262632).
    - CVE-2026-5773: wrong reuse of SMB connection (bsc#1262633).
    - CVE-2026-6253: proxy credentials leak over redirect-to proxy (bsc#1262635).
    - CVE-2026-6276: stale custom cookie host causes cookie leak (bsc#1262636).
    - CVE-2026-6429: netrc credential leak with reused proxy connection (bsc#1262638).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of Tenable Identity Exposure running on the remote host is prior to 3.93.5. It is, therefore, affected by multiple vulnerabilities according to advisory TNS-2026-16:

  - Tenable Identity Exposure contains multiple unauthenticated API endpoints under /w/api/* that expose     sensitive application configuration data including cleartext LDAP credentials, SAML configuration, user     accounts, and directory settings to unauthenticated remote attackers. Affected responses are served with     Cache-Control: public headers and without Vary: Cookie, allowing reverse proxies and CDNs to cache and     serve sensitive data to unauthenticated users even after authentication is applied. (CVE-2026-13007)

  - Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows     an authorized attacker to bypass a security feature over a network. (CVE-2025-55315)

  - Converting an excessively large OCTET STRING value to a hexadecimal string leads to a heap buffer     overflow on 32 bit platforms. A heap buffer overflow may lead to a crash or possibly an attacker     controlled code execution or other undefined behavior. (CVE-2026-31789)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

An update of the curl package has been released.

The remote Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8227-1 advisory.

    It was discovered that curl incorrectly reused non-TLS connections when TLS was required in some STARTTLS     configurations. A remote attacker could possibly use this issue to obtain sensitive information.
    (CVE-2026-4873)

    It was discovered that curl incorrectly reused certain HTTP Negotiate connections. A remote attacker could     possibly use this issue to obtain sensitive information. (CVE-2026-5545)

    It was discovered that curl incorrectly reused certain SMB connections. A remote attacker could possibly     use this issue to obtain sensitive information. (CVE-2026-5773)

    It was discovered that curl could leak proxy credentials when handling redirects in some configurations. A     remote attacker could possibly use this issue to obtain sensitive information. (CVE-2026-6253)

    It was discovered that curl could leak cookies because of stale custom cookie host handling in some     requests. A remote attacker could possibly use this issue to obtain sensitive information. (CVE-2026-6276)

    It was discovered that curl could leak .netrc credentials when reusing proxy connections in some     situations. A remote attacker could possibly use this issue to obtain sensitive information.
    (CVE-2026-6429)

    It was discovered that curl could leak Digest authentication state when switching proxies in some     situations. A remote attacker could possibly use this issue to obtain sensitive information.
    (CVE-2026-7168)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of curl installed on the remote host is 7.40.0 prior to 8.20.0. It is, therefore, affected by a wrong SMB connection reuse vulnerability:

  - libcurl might in some circumstances reuse the wrong connection for SMB(S) transfers. The code     erroneously did not consider the share name as a property to match for connection reuse, so subsequent     SMB transfers could incorrectly reuse connections intended for different shares on the same server.
    This could result in downloading incorrect files or uploading files to unintended locations.
    (CVE-2026-5773)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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 happens, the same credentials are used and the server name is the same. (CVE-2026-5773)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
326631	EulerOS 2.0 SP10 : curl (EulerOS-SA-2026-2684)	Nessus	Huawei Local Security Checks	high
326602	EulerOS 2.0 SP10 : curl (EulerOS-SA-2026-2644)	Nessus	Huawei Local Security Checks	high
326253	Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS / 24.04 LTS / 26.04 LTS : curl vulnerabilities (USN-8525-1)	Nessus	Ubuntu Local Security Checks	high
326141	EulerOS 2.0 SP12 : curl (EulerOS-SA-2026-2523)	Nessus	Huawei Local Security Checks	high
326110	EulerOS 2.0 SP12 : curl (EulerOS-SA-2026-2583)	Nessus	Huawei Local Security Checks	high
324850	SUSE SLES12 Security Update : curl (SUSE-SU-2026:2703-1)	Nessus	SuSE Local Security Checks	high
322483	Tenable Identity Exposure < 3.93.5 Multiple Vulnerabilities (TNS-2026-16)	Nessus	Misc.	high
313013	Photon OS 5.0: Curl PHSA-2026-5.0-0838	Nessus	PhotonOS Local Security Checks	high
313011	Photon OS 4.0: Curl PHSA-2026-4.0-1007	Nessus	PhotonOS Local Security Checks	high
312298	Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS : curl vulnerabilities (USN-8227-1)	Nessus	Ubuntu Local Security Checks	high
311423	Curl 7.40.0 < 8.20.0 Wrong SMB Connection Reuse	Nessus	Misc.	high
311011	Linux Distros Unpatched Vulnerability : CVE-2026-5773	Nessus	Misc.	high

Detections

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CVE-2026-5773

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Tenable Plugins

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