--- title: "CVE-2026-54886\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-2026-54886?format=md keywords: index, follow --- # CVE-2026-54886 Publication date 2 July 2026 Last updated 7 August 2026 --- Ubuntu priority **Medium** [Why this priority?](https://ubuntu.com/security/cves/about#priority ) ## Cvss 3 Severity Score **4.3 · Medium** [Score breakdown](https://ubuntu.com/security/CVE-2026-54886?format=md#impact-score) Toggle side navigation ## Description Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in Erlang OTP ssh (ssh\_sftpd module) allows an authenticated SFTP user to render an SFTP channel permanently unresponsive. The handle\_data/4 function in ssh\_sftpd contains a catch-all clause that accepts channel data of any type. When channel data with a non-zero type code (SSH\_MSG\_CHANNEL\_EXTENDED\_DATA) arrives with an empty pending buffer and a payload at or below the SFTP packet size limit, the clause tail-calls itself with identical arguments, creating an infinite loop. The SFTP protocol operates exclusively on normal channel data (type 0). Extended data (non-zero type) is meaningless for SFTP and is never sent by conforming clients. However, the SSH protocol permits any channel participant to send extended data on an open channel, so an authenticated SFTP client can trigger the loop by sending SSH\_MSG\_CHANNEL\_EXTENDED\_DATA with any data\_type\_code and any non-empty payload at or below the size limit. The targeted ssh\_sftpd process enters an infinite tail-recursive loop. It never processes another message, its message queue grows without bound, and it can only be stopped by killing the process. BEAM's reduction-based scheduler preemption continues to function, so other processes on the node are not starved, but each stuck channel process consumes its full CPU time share continuously and accumulates unbounded message queue memory. Opening many channels amplifies the CPU and memory impact. Erlang/OTP SSH configurations using the default max\_channels setting (infinity) allow an authenticated user to open unlimited channels per connection, amplifying the attack without requiring multiple TCP connections or authentications. No file contents, credentials, or write access are obtainable through this issue. The impact is limited to denial of service on targeted SFTP channels, with secondary CPU degradation and memory growth. This vulnerability is associated with program file lib/ssh/src/ssh\_sftpd.erl and program routine ssh\_sftpd:handle\_data/4. This issue affects OTP from OTP 17.0 before OTP 29.0.3, OTP 28.5.0.3 and OTP 27.3.4.14, corresponding to ssh from 3.0.1 before 6.0.2, 5.5.2.2 and 5.2.11.9. ## Status Show unmaintained releases | Package | Ubuntu Release | Status | | --- | --- | --- | | erlang | 26.04 LTS resolute | Needs evaluation | | 25.10 questing | Ignored end of life, was needs-triage | | 24.04 LTS noble | Needs evaluation | | 22.04 LTS jammy | Needs evaluation | | 20.04 LTS focal | Needs evaluation | | 18.04 LTS bionic | Needs evaluation | | 16.04 LTS xenial | Needs evaluation | | 14.04 LTS trusty | Needs evaluation | --- * [How can I get the fixes?](https://ubuntu.com/security/cves/about#security) * [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses) ## Severity score breakdown CVSS version: CVSS v4.0 [CVSS v4.0](https://ubuntu.com/security/CVE-2026-54886?format=md) [CVSS v3.0](https://ubuntu.com/security/CVE-2026-54886?format=md) **Base score** 5.3 · Medium * Base metrics | Parameter | Value | | --- | --- | | Attack vector | Network | | Attack complexity | Low | | Attack requirements | None | | Privileges required | Low | | User interaction | None | | Vulnerable system - Confidentiality impact | None | | Vulnerable system - Integrity impact | None | | Vulnerable system - Availability impact | Low | | Subsequent system - Confidentiality impact | None | | Subsequent system - Integrity impact | None | | Subsequent system - Availability impact | None | * Scores | Parameter | Value | | --- | --- | | Base score | 5.3 · Medium | | Base + Threat score | - | | Base + Environmental score | - | | Base + Threat + Environmental score | - | **Vector:** CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N ## References * [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-54886) * [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-54886) * [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-54886) * [Debian](https://security-tracker.debian.org/tracker/CVE-2026-54886) ### Other references * * * * * * *