CVE-2026-55581

HIGHPre-NVD 8.48.4—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 72% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
8.4EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.4Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

mcp-shell is an MCP server for running shell commands securely, auditably, and on demand. Prior to 0.6.0, the default Docker security.yaml includes /bin/bash in allowed_executables, while security.go validates only the first token and checkBlockedPatternsAndCommands does not reject the shell command-mode flag -c. A caller of the shell_exec MCP tool can provide the command argument /bin/bash -c , which passes validation and reaches executor.go, where parseCommand and exec.CommandContext execute the arbitrary command as mcpuser outside the intended allowlist. This issue is fixed in version 0.6.0.

CVSS v3
8.4
EG Score
8.4(medium)
EG Risk
54(Track*)
EG Risk 54/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity84% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
0%
EPSS %ILE
28%
KEV
Not listed

Published

August 25, 2026

Last Modified

September 9, 2026

Advisory Details (4)

Auto-updated Aug 25, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_commit, github_pr, github_release.
github Patch Available🟡 PoC Available

Secure Mode Allowlist Bypass via Default `/bin/bash` Executable · Advisory · sonirico/mcp-shell · GitHub

https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3
github_release Patch Available

v0.6.0 — secure mode by default

Patch available: sonirico/mcp-shell v0.6.0

https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0
github_pr Patch Available

fix: secure mode by default + keep interpreters out of the allowlist

Patch available: sonirico/mcp-shell v0.6.0 (PR #16 merged 2026-06-14)

https://github.com/sonirico/mcp-shell/pull/16
github_commit Patch Available

commit f31377fce6ec (sonirico/mcp-shell)

Patch available: sonirico/mcp-shell v0.6.0 (contains commit f31377fce6ec)

https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f

Vendor Advisories for CVE-2026-55581(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
Go(1)
PackageVulnerable rangeFixed inDependents
github.com/sonirico/mcp-shell—0.6.0—

Weakness Classification(3)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 13× in last 7d / 48× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-18 19:38 UTCEG score recompute
  2. 2026-09-18 19:28 UTCEPSS rescore
  3. 2026-09-17 21:08 UTCEG score recompute
  4. 2026-09-17 19:31 UTCEPSS rescore
  5. 2026-09-16 22:40 UTCEG score recompute
  6. 2026-09-16 14:08 UTCEPSS rescore
  7. 2026-09-16 10:49 UTCEG score recompute
  8. 2026-09-16 05:15 UTCEPSS rescore
  9. 2026-09-15 12:12 UTCEG score recompute
  10. 2026-09-15 03:11 UTCEPSS rescore
  11. 2026-09-14 02:21 UTCEG score recompute
  12. 2026-09-13 16:47 UTCEPSS rescore
  13. 2026-09-12 16:40 UTCEG score recompute
  14. 2026-09-11 18:13 UTCEG score recompute
  15. 2026-09-11 14:53 UTCEPSS rescore
  16. 2026-09-10 19:45 UTCEG score recompute
  17. 2026-09-10 09:35 UTCEPSS rescore
  18. 2026-09-09 01:14 UTCEG score recompute
  19. 2026-09-08 22:01 UTCEPSS rescore
  20. 2026-09-08 02:31 UTCEG score recompute
  21. 2026-09-07 16:01 UTCEPSS rescore
  22. 2026-09-06 15:41 UTCEG score recompute
  23. 2026-09-06 13:47 UTCEPSS rescore
  24. 2026-09-05 17:14 UTCEG score recompute
  25. 2026-09-04 18:45 UTCEG score recompute
Show 23 more
  1. 2026-09-04 07:10 UTCEG score recompute
  2. 2026-09-04 05:06 UTCEPSS rescore
  3. 2026-09-02 20:43 UTCEG score recompute
  4. 2026-09-02 14:12 UTCEPSS rescore
  5. 2026-09-01 20:11 UTCEG score recompute
  6. 2026-09-01 13:54 UTCEPSS rescore
  7. 2026-09-01 08:56 UTCEG score recompute
  8. 2026-09-01 04:40 UTCEPSS rescore
  9. 2026-08-30 23:09 UTCEG score recompute
  10. 2026-08-30 19:17 UTCEPSS rescore
  11. 2026-08-30 11:56 UTCEG score recompute
  12. 2026-08-30 01:22 UTCEPSS rescore
  13. 2026-08-29 02:12 UTCEG score recompute
  14. 2026-08-28 21:41 UTCEPSS rescore
  15. 2026-08-27 16:20 UTCEG score recompute
  16. 2026-08-27 14:25 UTCEPSS rescore
  17. 2026-08-26 17:51 UTCEG score recompute
  18. 2026-08-26 14:46 UTCEPSS rescore
  19. 2026-08-26 06:35 UTCEG score recompute
  20. 2026-08-25 19:21 UTCEG score recompute
  21. 2026-08-25 19:10 UTCEG score recompute
  22. 2026-08-25 16:23 UTCEG score recompute
  23. 2026-08-25 15:44 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55581?
CVE-2026-55581 is a high vulnerability published on August 25, 2026. mcp-shell is an MCP server for running shell commands securely, auditably, and on demand. Prior to 0.6.0, the default Docker security.yaml includes /bin/bash in allowedexecutables, while security.go validates only the first token and checkBlockedPatternsAndCommands does not reject the shell…
When was CVE-2026-55581 disclosed?
CVE-2026-55581 was first published in the National Vulnerability Database on August 25, 2026, with the most recent update on September 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55581 actively exploited?
CVE-2026-55581 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 72.4% of all scored CVEs.
What is the CVSS score of CVE-2026-55581?
CVE-2026-55581 has a CVSS v3 base score of 8.4 (NVD).
How do I remediate CVE-2026-55581?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55581, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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