Is CVE-2026-23943 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-23943 being exploited in the wild.

How severe is CVE-2026-23943?

Medium severity, with a CVSS score of 5.3, published 13 March 2026.

Which products and versions are affected?

Erlang OTP 17.0 to 26.2.5.17, 27.0 to 27.3.4.8, 28.0 to 28.4.0; Erlang ssh 3.0.1 to 5.1.4.13, 5.2 to 5.2.11.5, 5.5 to 5.5.0.

Is there a fix for CVE-2026-23943?

A patch was published on 2026-03-12: Fixes merged into maintenance branches. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-23943 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-23943?

Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-23943: Erlang OTP SSH denial of service via zlib compression bomb

CVE-2026-23943 · Severity: medium · CVSS 5.3 · Published 2026-03-13

A vulnerability in the Erlang SSH library allows an attacker to crash or disable services by sending specially crafted, highly compressed data. This 'compression bomb' can exhaust a server's memory, leading to a denial of service that prevents legitimate users from accessing the system. Because the flaw can be triggered before a user even logs in, it poses a significant risk to any publicly accessible Erlang-based SSH service.

Quick answers

Is CVE-2026-23943 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-23943 being exploited in the wild.
How severe is CVE-2026-23943?: Medium severity, with a CVSS score of 5.3, published 13 March 2026.
Which products and versions are affected?: Erlang OTP 17.0 to 26.2.5.17, 27.0 to 27.3.4.8, 28.0 to 28.4.0; Erlang ssh 3.0.1 to 5.1.4.13, 5.2 to 5.2.11.5, 5.5 to 5.5.0.
Is there a fix for CVE-2026-23943?: A patch was published on 2026-03-12: Fixes merged into maintenance branches. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-23943 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-23943?: Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The Erlang OTP SSH transport layer (ssh_transport modules) fails to impose size limits on decompressed data when using zlib compression. An attacker can send a 'compression bomb'—a small payload that expands significantly upon decompression (up to a 1029:1 ratio)—to trigger an Out-of-Memory (OOM) condition. The 'zlib' algorithm is enabled by default and operates pre-authentication, allowing unauthenticated remote attackers to exhaust memory. The 'zlib@openssh.com' algorithm is also affected but requires successful authentication. The issue is fixed in OTP versions 28.4.1, 27.3.4.9, and 26.2.5.18 by disabling zlib by default and implementing decompression size limits.

Affected products

Erlang OTP 17.0 to 26.2.5.17, 27.0 to 27.3.4.8, 28.0 to 28.4.0
Erlang ssh 3.0.1 to 5.1.4.13, 5.2 to 5.2.11.5, 5.5 to 5.5.0

Timeline

2026-03-12: patched: Fixes merged into maintenance branches.
2026-03-13: disclosed: Initial vulnerability disclosure.
2026-03-13: advisory: NVD and Vendor advisories published.

References

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