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

The remote SUSE Linux SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:1940-1 advisory.

    Security issues fixed:

    - CVE-2026-4873: connection reuse ignores TLS requirement (bsc#1262631).
    - CVE-2026-5545: wrong reuse of HTTP Negotiate connection (bsc#1262632).
    - 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).

    Other updates and bugfixes:

    - sws: prevent 'connection monitor' to say disconnect twice (bsc#1259362).

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 remote SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:1717-1 advisory.

    Security issues fixed:

    - CVE-2026-4873: connection reuse ignores TLS requirement (bsc#1262631).
    - CVE-2026-5545: wrong reuse of HTTP Negotiate connection (bsc#1262632).
    - 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).

    Other updates and bugfixes:

    - sws: prevent 'connection monitor' to say disconnect twice (bsc#1259362).

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.

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 7.14.1 prior to 8.20.0. It is, therefore, affected by a proxy credential disclosure vulnerability:

  - curl might erroneously pass on credentials for a first proxy to a second proxy. This flaw occurs when     different proxies are configured for different URL schemes, the first proxy requires authentication,     the second proxy does not need credentials, and a redirect occurs from one URL scheme to another. The     credentials are transmitted in base64-encoded form to the unintended proxy. (CVE-2026-6253)

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.

  - 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)

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

ID	Name	Product	Family	Severity
315269	SUSE SLES15 Security Update : curl (SUSE-SU-2026:1940-1)	Nessus	SuSE Local Security Checks	medium
313680	SUSE SLED15 / SLES15 Security Update : curl (SUSE-SU-2026:1717-1)	Nessus	SuSE Local Security Checks	medium
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
311419	Curl 7.14.1 < 8.20.0 Proxy Credential Disclosure	Nessus	Misc.	medium
311014	Linux Distros Unpatched Vulnerability : CVE-2026-6253	Nessus	Misc.	medium

Detections

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CVE-2026-6253

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