CVE-2026-23943
CVE-2026-23943 · Pre-auth SSH DoS via unbounded zlib inflate
This page contains facts from public vulnerability sources. Check the original advisory before updating.
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 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.
CVSS 6.9 · Medium · EPSS 0.7% · Fix available
- Published
- Updated
Stack: system
Affected products and versions
erlang
- Versions
- ≥ 3.0.1: Affected; ≥ 5.5.1: Not affected; ≥ 5.2.11.6: Not affected; ≥ 5.1.4.14: Not affected (otp)
Update to 5.1.4.14
erlang
- Versions
- ≥ 17.0: Affected; ≥ 28.4.1: Not affected; ≥ 27.3.4.9: Not affected; ≥ 26.2.5.18: Not affected (otp)
- ≥ 07b8f441ca711f9812fad9e9115bab3c3aa92f79: Affected; ≥ 43a87b949bdff12d629a8c34146711d9da93b1b1: Not affected; ≥ 93073c3bd338c60cd2bae715ce6a1d4ffc1a8fd3: Not affected; ≥ 0c1c04b191f6ab940e8fcfabce39eb5a8a6440a4: Not affected (git)
Update to 26.2.5.18
erlang Debian:12
- Versions
- 1:25.2.3+dfsg-1
- 1:25.2.3+dfsg-1+deb12u1
- 1:25.2.3+dfsg-1+deb12u2
- 1:25.2.3+dfsg-1+deb12u3
- Affected ranges
- ECOSYSTEM: < 1:25.2.3+dfsg-1+deb12u4
Update to 1:25.2.3+dfsg-1+deb12u4
erlang Debian:13
- Versions
- 1:27.3.4.1+dfsg-1
- 1:27.3.4.1+dfsg-1+deb13u1
- Affected ranges
- ECOSYSTEM: < 1:27.3.4.1+dfsg-1+deb13u2
Update to 1:27.3.4.1+dfsg-1+deb13u2
erlang Debian:14
- Versions
- 1:27.3.4.1+dfsg-1
- 1:27.3.4.3+dfsg-1
- 1:27.3.4.4+dfsg-1
- 1:27.3.4.6+dfsg-1
- 1:27.3.4.8+dfsg-1
- Affected ranges
- ECOSYSTEM: < 1:27.3.4.9+dfsg-1
Update to 1:27.3.4.9+dfsg-1
erlang Ubuntu:Pro:14.04:LTS
- Versions
- 1:16.b.1-dfsg-4ubuntu1
- 1:16.b.2-dfsg-1ubuntu1
- 1:16.b.2-dfsg-2ubuntu1
- 1:16.b.3-dfsg-1ubuntu1
- 1:16.b.3-dfsg-1ubuntu2
- 1:16.b.3-dfsg-1ubuntu2.1
- 1:16.b.3-dfsg-1ubuntu2.2
- 1:16.b.3-dfsg-1ubuntu2.2+esm1
- 1:16.b.3-dfsg-1ubuntu2.2+esm2
- Affected ranges
- ECOSYSTEM: < 1:16.b.3-dfsg-1ubuntu2.2+esm3
Update to 1:16.b.3-dfsg-1ubuntu2.2+esm3
erlang Ubuntu:Pro:16.04:LTS
- Versions
- 1:18.0-dfsg-1ubuntu1
- 1:18.0-dfsg-1ubuntu2
- 1:18.2-dfsg-2ubuntu1
- 1:18.3-dfsg-1ubuntu1
- 1:18.3-dfsg-1ubuntu2
- 1:18.3-dfsg-1ubuntu3
- 1:18.3-dfsg-1ubuntu3.1
- 1:18.3-dfsg-1ubuntu3.1+esm1
- 1:18.3-dfsg-1ubuntu3.1+esm2
- 1:18.3-dfsg-1ubuntu3.1+esm3
- Affected ranges
- ECOSYSTEM: < 1:18.3-dfsg-1ubuntu3.1+esm4
Update to 1:18.3-dfsg-1ubuntu3.1+esm4
erlang Ubuntu:Pro:18.04:LTS
- Versions
- 1:20.0.4+dfsg-1ubuntu1
- 1:20.1.2+dfsg-1ubuntu1
- 1:20.1.3+dfsg-1ubuntu1
- 1:20.1.4+dfsg-1ubuntu1
- 1:20.1.5+dfsg-1ubuntu1
- 1:20.1.6+dfsg-1ubuntu1
- 1:20.1.7+dfsg-1ubuntu1
- 1:20.2.1+dfsg-1ubuntu1
- 1:20.2.2+dfsg-1ubuntu1
- 1:20.2.2+dfsg-1ubuntu2
- 1:20.2.2+dfsg-1ubuntu2+esm1
- 1:20.2.2+dfsg-1ubuntu2+esm2
- 1:20.2.2+dfsg-1ubuntu2+esm3
- Affected ranges
- ECOSYSTEM: < 1:20.2.2+dfsg-1ubuntu2+esm4
Update to 1:20.2.2+dfsg-1ubuntu2+esm4
erlang Ubuntu:Pro:20.04:LTS
- Versions
- 1:22.0.7+dfsg-1build1
- 1:22.2+dfsg-1
- 1:22.2.1+dfsg-1
- 1:22.2.2+dfsg-1
- 1:22.2.3+dfsg-1
- 1:22.2.3+dfsg-2
- 1:22.2.4+dfsg-1
- 1:22.2.7+dfsg-1
- 1:22.2.7+dfsg-1ubuntu0.2
- 1:22.2.7+dfsg-1ubuntu0.3
- 1:22.2.7+dfsg-1ubuntu0.4
- 1:22.2.7+dfsg-1ubuntu0.5
- 1:22.2.7+dfsg-1ubuntu0.5+esm1
- 1:22.2.7+dfsg-1ubuntu0.5+esm2
- Affected ranges
- ECOSYSTEM: < 1:22.2.7+dfsg-1ubuntu0.5+esm3
Update to 1:22.2.7+dfsg-1ubuntu0.5+esm3
erlang Ubuntu:22.04:LTS
- Versions
- 1:23.2.6+dfsg-1build1
- 1:24.1.1+dfsg-1
- 1:24.1.4+dfsg-1
- 1:24.1.5+dfsg-1
- 1:24.1.5+dfsg-1ubuntu1
- 1:24.2+dfsg-1
- 1:24.2.1+dfsg-1
- 1:24.2.1+dfsg-1ubuntu0.1
- 1:24.2.1+dfsg-1ubuntu0.2
- 1:24.2.1+dfsg-1ubuntu0.3
- 1:24.2.1+dfsg-1ubuntu0.4
- 1:24.2.1+dfsg-1ubuntu0.5
- 1:24.2.1+dfsg-1ubuntu0.6
- 1:24.2.1+dfsg-1ubuntu0.7
- Affected ranges
- ECOSYSTEM: < 1:24.2.1+dfsg-1ubuntu0.8
Update to 1:24.2.1+dfsg-1ubuntu0.8
erlang Ubuntu:24.04:LTS
- Versions
- 1:25.2.3+dfsg-1
- 1:25.3.2.8+dfsg-1
- 1:25.3.2.8+dfsg-1ubuntu1
- 1:25.3.2.8+dfsg-1ubuntu3
- 1:25.3.2.8+dfsg-1ubuntu4
- 1:25.3.2.8+dfsg-1ubuntu4.1
- 1:25.3.2.8+dfsg-1ubuntu4.2
- 1:25.3.2.8+dfsg-1ubuntu4.3
- 1:25.3.2.8+dfsg-1ubuntu4.4
- 1:25.3.2.8+dfsg-1ubuntu4.5
- 1:25.3.2.8+dfsg-1ubuntu4.6
- 1:25.3.2.8+dfsg-1ubuntu4.7
- Affected ranges
- ECOSYSTEM: < 1:25.3.2.8+dfsg-1ubuntu4.8
Update to 1:25.3.2.8+dfsg-1ubuntu4.8
erlang Ubuntu:25.10
- Versions
- 1:27.3+dfsg-1ubuntu1
- 1:27.3+dfsg-1ubuntu1.1
- 1:27.3.4.1+dfsg-1
- 1:27.3.4.1+dfsg-1build1
- 1:27.3.4.1+dfsg-1ubuntu0.1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
erlang Ubuntu:26.04:LTS
- Versions
- 1:27.3.4.1+dfsg-1build1
- 1:27.3.4.3+dfsg-1
- 1:27.3.4.4+dfsg-1
- 1:27.3.4.6+dfsg-1
- 1:27.3.4.6+dfsg-1ubuntu0.1
- Affected ranges
- ECOSYSTEM: < 1:27.3.4.6+dfsg-1ubuntu0.2
Update to 1:27.3.4.6+dfsg-1ubuntu0.2
Original sources
- 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
- https://nvd.nist.gov/vuln/detail/CVE-2026-23943