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: 0.5% (37th percentile of EPSS-scored CVEs). 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: 0.5%CVSS: 8.4Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

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
8.4HIGHmedium confidence
EG Risk
54
EG Risk 54/100CISA SSVC

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%
CISA SSVC: Track at low, Track* at medium and Attend at high mission impact.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.5%
EPSS %ILE
37th
KEV
Not listed

CISA SSVCTrack at low, Track* at medium and Attend at high mission impact.

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

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.
githubMentions a patch (unverified)🟡 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 rangeFix by version rangeDependents
github.com/sonirico/mcp-shell—
  • every version up to 0.6.0: fixed in 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 / 54× 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. 2026-10-10 20:00 UTCEPSS rescore
  2. 2026-10-10 12:02 UTCEG score recompute
  3. 2026-10-09 20:07 UTCEPSS rescore
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  1. 2026-09-28 13:51 UTCEPSS rescore
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  4. 2026-09-26 22:05 UTCEG score recompute
  5. 2026-09-26 15:59 UTCEPSS rescore
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  8. 2026-09-23 23:34 UTCEG score recompute
  9. 2026-09-23 17:54 UTCEPSS rescore
  10. 2026-09-23 01:02 UTCEG score recompute
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  13. 2026-09-20 20:16 UTCEPSS rescore
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  26. 2026-09-13 16:47 UTCEPSS rescore
  27. 2026-09-12 16:40 UTCEG score recompute
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  29. 2026-09-11 14:53 UTCEPSS rescore
  30. 2026-09-10 19:45 UTCEG score recompute
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  37. 2026-09-06 13:47 UTCEPSS rescore
  38. 2026-09-05 17:14 UTCEG score recompute
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  40. 2026-09-04 07:10 UTCEG score recompute
  41. 2026-09-04 05:06 UTCEPSS rescore
  42. 2026-09-02 20:43 UTCEG score recompute
  43. 2026-09-02 14:12 UTCEPSS rescore
  44. 2026-09-01 20:11 UTCEG score recompute
  45. 2026-09-01 13:54 UTCEPSS rescore
  46. 2026-09-01 08:56 UTCEG score recompute
  47. 2026-09-01 04:40 UTCEPSS rescore
  48. 2026-08-30 23:09 UTCEG score recompute
  49. 2026-08-30 19:17 UTCEPSS rescore
  50. 2026-08-30 11:56 UTCEG score recompute
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  53. 2026-08-28 21:41 UTCEPSS rescore
  54. 2026-08-27 16:20 UTCEG score recompute
  55. 2026-08-27 14:25 UTCEPSS rescore
  56. 2026-08-26 17:51 UTCEG score recompute
  57. 2026-08-26 14:46 UTCEPSS rescore
  58. 2026-08-26 06:35 UTCEG score recompute
  59. 2026-08-25 19:21 UTCEG score recompute
  60. 2026-08-25 19:10 UTCEG score recompute
  61. 2026-08-25 16:23 UTCEG score recompute
  62. 2026-08-25 15:44 UTCEG score recompute

Related CVEs(same product + same CWE)

Same product

2 shown

Go:github.com/sonirico/mcp-shell

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 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 0.5% probability of exploitation in the next 30 days (37th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55581?
CVE-2026-55581 has a CVSS base score of 8.4 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55581?
A fix for CVE-2026-55581 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-55581 are linked in the Vendor Advisories panel on this page.

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