ConnectBot SSH Client Library: Unbounded SSH field lengths can cause excessive memory allocation

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.9 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-54700: 0.37% estimated exploitation activity in the next 30 days; percentile 30.93 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The SSH protocol parser trusted attacker-controlled length and count fields without first checking that the declared values fit within the containing packet. When a client connects to a malicious or compromised SSH server, the server can send a small, malformed packet containing an inner field whose declared length is much larger than the packet itself. The Kaitai Struct Java runtime attempts to allocate a byte array using the declared length before it discovers that the input is truncated. A sufficiently large value can therefore cause excessive memory allocation or an uncaught OutOfMemoryError, potentially terminating the application process that uses the library. Applications that enable SSH agent forwarding have an additional attack path: the connected server can send malformed agent protocol messages containing the same class of oversized inner length. Details SSH uses unsigned 32-bit length prefixes for strings and other protocol structures. Before the fix, several…

Published by the source

12 Jun 2026, 21:02 UTC

Last modified by the source

8 Jul 2026, 17:35 UTC

Source last checked

26 Oct 2026, 16:54 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-ch3q-cw5r-f4hg

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# Patch Next advisory brief: CVE-2026-54700

Advisory: ConnectBot SSH Client Library: Unbounded SSH field lengths can cause excessive memory allocation
IDs: CVE-2026-54700, GHSA-ch3q-cw5r-f4hg
Record: https://patchnext.com/advisories/cve-2026-54700 (revision 1, source checked 26 Oct 2026, 16:54 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.connectbot.sshlib:sshlib: affected <= 0.3.0

## Suggested inspection (read-only)
- Maven org.connectbot.sshlib:sshlib: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.connectbot.sshlib:sshlib.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-ch3q-cw5r-f4hg (GitHub-reviewed advisory GHSA-ch3q-cw5r-f4hg lists affected ranges: Maven org.connectbot.sshlib:sshlib >=0 <=0.3.0)

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