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.

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.

The version of libcurl installed on the remote host is 8.18.0 prior to 8.21.0. It is, therefore, affected by a denial of service vulnerability:

  - 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. (CVE-2026-11352)

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

The version of curl installed on the remote host is 8.18.0 prior to 8.21.0. It is, therefore, affected by a denial of service vulnerability:

  - An issue in curl's QUIC UDP receive function allows a malicious HTTP/3 server to trigger a remote denial     of service by continuously streaming empty datagrams to indefinitely stall the client.
    (CVE-2026-11352)

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.

  - 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. (CVE-2026-11352)

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

ID	Name	Product	Family	Severity
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
326238	libcurl 8.18.0 < 8.21.0 QUIC UDP Denial of Service (CVE-2026-11352)	Nessus	Misc.	high
323015	Curl 8.18.0 < 8.21.0 QUIC Zero-Length UDP Datagrams DoS	Nessus	Misc.	high
322461	Linux Distros Unpatched Vulnerability : CVE-2026-11352	Nessus	Misc.	high

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