--- title: "CVE-2026-75804\n | Ubuntu" description: Ubuntu is an open source software operating system that runs from the desktop, to the cloud, to all your internet connected things. url: https://ubuntu.com/security/CVE-2026-75804?format=md keywords: index, follow --- # CVE-2026-75804 Publication date 29 September 2026 Last updated 30 September 2026 --- Ubuntu priority **Low** [Why this priority?](https://ubuntu.com/security/CVE-2026-75804?format=md#priority-reason ) ## Cvss 3 Severity Score **5.3 · Medium** [Score breakdown](https://ubuntu.com/security/CVE-2026-75804?format=md#impact-score) Toggle side navigation ## Description Issue summary: OpenSSL QUIC stack does not enforce connection level flow control for streams. Remote peers may send more bytes as long as they fit within the stream flow control limits. Impact summary: A malicious remote peer may exploit the lack of connection flow control for streams to make the QUIC stack receive ~100MB of memory instead of 768 KiB (default flow control window size). CWE: CWE-770: Allocation of Resources Without Limits or Throttling Description: The local QUIC stack advertises two flow control limits to its remote peer: stream flow control limit and connection flow control limit. The remote peer must follow both limits when transmitting stream data. Whenever the local QUIC stack receives a stream frame, it validates that the size of the received stream frame stays within flow control limits. If either limit is exceeded (stream level or connection level), then the QUIC stack must close the connection with a flow control error. The vulnerable OpenSSL QUIC stack enforces the stream-level but not the connection-level limit. To exploit the issue, three conditions must be met: - the remote peer opens several streams - each stream must stay within the stream-level flow control limit - there must be no zero-offset byte sent on any of the streams (to prevent the vulnerable QUIC stack from consuming data). By meeting the conditions above, the remote peer may make the local stack allocate 2 x MAX\_STREAMS x (stream flow control limit) bytes of memory. MAX\_STREAMS defaults to 100, and the limit applies to both bidirectional and unidirectional streams, making it 200 in total. The default flow control window for a stream is 512kB. The remote peer may force the vulnerable QUIC stack to allocate 100MB of heap per connection. FIPS impact: no The FIPS module is not affected as the QUIC implementation is outside of the OpenSSL FIPS module boundary. [Read the notes from the security team](https://ubuntu.com/security/CVE-2026-75804?format=md#notes) ### Why is this CVE low priority? OpenSSL developers have rated this issue as being low severity [Learn more about Ubuntu priority](https://ubuntu.com/security/cves/about#priority) ## Status Show unmaintained releases | Package | Ubuntu Release | Status | | --- | --- | --- | | openssl | 26.04 LTS resolute | Fixed 3.5.5-1ubuntu3.6 | | 24.04 LTS noble | Not affected | | 22.04 LTS jammy | Not affected | | 20.04 LTS focal | Not affected | | 18.04 LTS bionic | Not affected | | 16.04 LTS xenial | Not affected | | 14.04 LTS trusty | Not affected | | openssl-fips | 26.04 LTS resolute | Not in release | | 24.04 LTS noble FIPS Updates | Not affected | | 22.04 LTS jammy FIPS Updates | Not affected | | openssl1.0 | 26.04 LTS resolute | Not in release | | 24.04 LTS noble | Not in release | | 22.04 LTS jammy | Not in release | | 18.04 LTS bionic | Not affected | | nodejs | 26.04 LTS resolute | Not affected | | 24.04 LTS noble | Not affected | | 22.04 LTS jammy | Vulnerable | | 20.04 LTS focal | Not affected | | 18.04 LTS bionic | Not affected | | 16.04 LTS xenial | Not affected | | 14.04 LTS trusty | Not affected | | edk2 | 26.04 LTS resolute | Vulnerable | | 24.04 LTS noble | Not affected | | 22.04 LTS jammy | Not affected | | 20.04 LTS focal | Not affected | | 18.04 LTS bionic | Not affected | | 16.04 LTS xenial | Not affected | | edk2-hwe | 26.04 LTS resolute | Vulnerable | | 24.04 LTS noble | Not in release | | 22.04 LTS jammy | Not in release | --- * [How can I get the fixes?](https://ubuntu.com/security/cves/about#security) * [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses) ## Notes --- ### [mdeslaur](https://launchpad.net/~mdeslaur) edk2 in jammy embeds OpenSSL 1.1.1j edk2 in noble embeds OpenSSL 3.0.9 edk2 in resolute embeds OpenSSL 3.5.1 edk2 in stonking embeds OpenSSL 3.5.1 nodejs in jammy embeds OpenSSL 1.1.1m 4.0, 3.6, 3.5, 3.4 are vulnerable ## Severity score breakdown CVSS version: CVSS v3.0 **Base score** 5.3 · Medium * Base metrics | Parameter | Value | | --- | --- | | Attack vector | Network | | Attack complexity | Low | | Privileges required | None | | User interaction | None | | Scope | Unchanged | | Confidentiality impact | None | | Integrity impact | None | | Availability impact | Low | * Scores | Parameter | Value | | --- | --- | | Base score | 5.3 · Medium | | Exploitability score | - | | Impact score | - | **Vector:** CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L ## References * [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-75804) * [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-75804) * [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-75804) * [Debian](https://security-tracker.debian.org/tracker/CVE-2026-75804) ### Related Ubuntu Security Notices (USN) + [USN-8847-1](https://usn.ubuntu.com/USN-8847-1) + OpenSSL vulnerabilities + 29 September 2026 ### Other references * *