CVE-2026-23943
Pre-auth SSH DoS via unbounded zlib inflate
Description
Improper Handling of Highly Compressed Data (Compression Bomb) vulnerability in Erlang OTP ssh (ssh_transport modules) allows Denial of Service via Resource Depletion. The SSH transport layer advertises legacy zlib compression by default and inflates attacker-controlled payloads pre-authentication without any size limit, enabling reliable memory exhaustion DoS. Two compression algorithms are affected: * zlib: Activates immediately after key exchange, enabling unauthenticated attacks * [email protected]: Activates post-authentication, enabling authenticated attacks Each SSH packet can decompress ~255 MB from 256 KB of wire data (1029:1 amplification ratio). Multiple packets can rapidly exhaust available memory, causing OOM kills in memory-constrained environments. This vulnerability is associated with program files lib/ssh/src/ssh_transport.erl and program routines ssh_transport:decompress/2, ssh_transport:handle_packet_part/4. This issue affects OTP from OTP 17.0 until OTP 28.4.1, 27.3.4.9 and 26.2.5.18 corresponding to ssh from 3.0.1 until 5.5.1, 5.2.11.6 and 5.1.4.14.
INFO
Published Date :
March 13, 2026, 7:54 p.m.
Last Modified :
May 21, 2026, 3:22 p.m.
Remotely Exploit :
Yes !
Source :
6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Affected Products
The following products are affected by CVE-2026-23943
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 4.0 | MEDIUM | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db |
Solution
- Update Erlang OTP to a patched version.
- Disable zlib compression if updating is not possible.
- Configure SSH to limit compressed payload sizes.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-23943.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-23943 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-23943
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-23943 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-23943 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
May. 21, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L Added CPE Configuration OR *cpe:2.3:a:erlang:erlang/otp:*:*:*:*:*:*:*:* versions from (including) 17.0 up to (excluding) 26.2.5.18 *cpe:2.3:a:erlang:erlang/otp:*:*:*:*:*:*:*:* versions from (including) 27.0 up to (excluding) 27.3.4.9 *cpe:2.3:a:erlang:erlang/otp:*:*:*:*:*:*:*:* versions from (including) 28.0 up to (excluding) 28.4.1 *cpe:2.3:a:erlang:erlang/ssh:*:*:*:*:*:*:*:* versions from (including) 3.0.1 up to (excluding) 5.1.4.14 *cpe:2.3:a:erlang:erlang/ssh:*:*:*:*:*:*:*:* versions from (including) 5.2 up to (excluding) 5.2.11.6 *cpe:2.3:a:erlang:erlang/ssh:*:*:*:*:*:*:*:* versions from (including) 5.5 up to (including) 5.5.1 Added Reference Type EEF: https://cna.erlef.org/cves/CVE-2026-23943.html Types: Vendor Advisory Added Reference Type EEF: https://github.com/erlang/otp/commit/0c1c04b191f6ab940e8fcfabce39eb5a8a6440a4 Types: Patch Added Reference Type EEF: https://github.com/erlang/otp/commit/43a87b949bdff12d629a8c34146711d9da93b1b1 Types: Patch Added Reference Type EEF: https://github.com/erlang/otp/commit/93073c3bd338c60cd2bae715ce6a1d4ffc1a8fd3 Types: Patch Added Reference Type EEF: https://github.com/erlang/otp/security/advisories/GHSA-c836-qprm-jw9r Types: Vendor Advisory Added Reference Type EEF: https://osv.dev/vulnerability/EEF-CVE-2026-23943 Types: Third Party Advisory Added Reference Type EEF: https://www.erlang.org/doc/system/versions.html#order-of-versions Types: Product -
CVE Modified by 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Apr. 06, 2026
Action Type Old Value New Value Added Reference https://cna.erlef.org/cves/CVE-2026-23943.html Added Reference https://osv.dev/vulnerability/EEF-CVE-2026-23943 -
New CVE Received by 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Mar. 13, 2026
Action Type Old Value New Value Added Description Improper Handling of Highly Compressed Data (Compression Bomb) vulnerability in Erlang OTP ssh (ssh_transport modules) allows Denial of Service via Resource Depletion. The SSH transport layer advertises legacy zlib compression by default and inflates attacker-controlled payloads pre-authentication without any size limit, enabling reliable memory exhaustion DoS. Two compression algorithms are affected: * zlib: Activates immediately after key exchange, enabling unauthenticated attacks * [email protected]: Activates post-authentication, enabling authenticated attacks Each SSH packet can decompress ~255 MB from 256 KB of wire data (1029:1 amplification ratio). Multiple packets can rapidly exhaust available memory, causing OOM kills in memory-constrained environments. This vulnerability is associated with program files lib/ssh/src/ssh_transport.erl and program routines ssh_transport:decompress/2, ssh_transport:handle_packet_part/4. This issue affects OTP from OTP 17.0 until OTP 28.4.1, 27.3.4.9 and 26.2.5.18 corresponding to ssh from 3.0.1 until 5.5.1, 5.2.11.6 and 5.1.4.14. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-409 Added Reference https://github.com/erlang/otp/commit/0c1c04b191f6ab940e8fcfabce39eb5a8a6440a4 Added Reference https://github.com/erlang/otp/commit/43a87b949bdff12d629a8c34146711d9da93b1b1 Added Reference https://github.com/erlang/otp/commit/93073c3bd338c60cd2bae715ce6a1d4ffc1a8fd3 Added Reference https://github.com/erlang/otp/security/advisories/GHSA-c836-qprm-jw9r Added Reference https://www.erlang.org/doc/system/versions.html#order-of-versions