Microsoft security update for CVE-2026-54886 — azl3 erlang
🔗 CVE IDs covered (1)
📋 Microsoft's advisory
EchelonGraph does not copy Microsoft's advisory page: its FAQ and remediation text are not shown here. Read the advisory on https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-54886. This page also shows what EchelonGraph holds for CVE-2026-54886, with the description from its CVE record, which the CVE Numbering Authority that assigned the CVE wrote: for a CVE Microsoft assigned, often in the words of Microsoft's own advisory.
🎯 Affected products2
- azl3 erlang 26.2.5.21-2 on Azure Linux 3.0
- azl3 erlang 26.2.5.21-4 on Azure Linux 3.0
✅ Updates Microsoft lists: 2 updates
2 rows: one per KB article or update, update type and fixed build. Their details are on Microsoft's advisory.
| KB article | Update | Fixed build |
|---|---|---|
| — | Security Update | 26.2.5.21-3 |
| — | Security Update | 26.2.5.21-4 |
🧭 EchelonGraph on CVE-2026-54886
- EchelonGraph score
- 4.3 MEDIUM
- CISA KEV
- Not listed
- Fix status
- A fix is available — apply it.
Description from the CVE record (CVE.org), as published by its numbering authority
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 27.3.4.14, OTP 28.5.0.3, and OTP 29.0.3, corresponding to ssh from 3.0.1 before 5.2.11.9, 5.5.2.2, and 6.0.2. Whether OTP before OTP 17.0, corresponding to ssh before 3.0.1, is affected is unknown.
Published by Erlang Ecosystem Foundation, the CVE Numbering Authority that assigned CVE-2026-54886, in its CVE record at CVE.org; reused under the CVE Program's Terms of Use (its licence and MITRE's copyright notice are in our Terms of Service).