CVE-2026-23943
Pre-auth SSH DoS via unbounded zlib inflate
At a glance
- Source
- NVD
- EPSS
- EPSS 0.67 % · percentile 52 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- EEF
- NVD status
- Modified
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 * zlib@openssh.com: 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 before OTP 28.4.1, OTP 27.3.4.9 and OTP 26.2.5.18, corresponding to ssh from 3.0.1 before 5.5.1, 5.2.11.6 and 5.1.4.14.
Weaknesses (CWE)
- CWE-409 — Improper Handling of Highly Compressed Data (Data Amplification)
References
- https://github.com/erlang/otp/security/advisories/GHSA-c836-qprm-jw9r
- https://cna.erlef.org/cves/CVE-2026-23943.html
- https://osv.dev/vulnerability/EEF-CVE-2026-23943
- https://www.erlang.org/doc/system/versions.html#order-of-versions
- https://github.com/erlang/otp/commit/43a87b949bdff12d629a8c34146711d9da93b1b1
- https://github.com/erlang/otp/commit/93073c3bd338c60cd2bae715ce6a1d4ffc1a8fd3
- https://github.com/erlang/otp/commit/0c1c04b191f6ab940e8fcfabce39eb5a8a6440a4
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 4.0 | MEDIUM 6.9 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N | EEF |
| CVSS 4.0 | MEDIUM 6.9 | CVSS:4.0/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 | NVD · 6b3ad84c-e1a6-4bf7-a703-f496b71e49db (Secondary) |
| CVSS 3.1 | MEDIUM 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | NVD · nvd@nist.gov (Primary) |
European references
- ENISA EUVD · EUVD-2026-11780
- GCVE · GCVE-0-2026-23943
CERT-FR advisories
- CERTFR-2026-AVI-0436 — Multiples vulnérabilités dans Tenable Identity Exposure · cert.ssi.gouv.fr
- CERTFR-2026-AVI-0321 — Multiples vulnérabilités dans les produits Microsoft · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*≥ 17.0 < 26.2.5.18cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*≥ 27.0 < 27.3.4.9cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*≥ 28.0 < 28.4.1cpe:2.3:a:erlang:erlang\/ssh:*:*:*:*:*:*:*:*≥ 3.0.1 < 5.1.4.14cpe:2.3:a:erlang:erlang\/ssh:*:*:*:*:*:*:*:*≥ 5.2 < 5.2.11.6cpe:2.3:a:erlang:erlang\/ssh:*:*:*:*:*:*:*:*≥ 5.5 ≤ 5.5.1
Affected products
| Product | Versions |
|---|---|
| Erlang · OTP | affected 3.0.1 < * |
| Erlang · OTP | affected 17.0 < * ; affected 07b8f441ca711f9812fad9e9115bab3c3aa92f79 < * |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |