Credential ExfilPublished Mar 15, 2026

MCP server leaks GITHUB_TOKEN via error messages

HighAARM tierConfirmed
Seen45times across8customers
jiffy-ti-2026-000050

Summary

MCP server that, on error paths, includes the full environment in a verbose traceback returned to the agent. GitHub tokens and other secrets surface in the tool response body and are then cached in agent logs.

Severity & confidence

Severity
High

High

Credible abuse path with meaningful impact on confidentiality, integrity, or availability. Remediate on a short timeline; do not wait for the next sprint cycle.

Confidence
Confirmed

Confirmed

Observed directly by Jiffy scanners or validated by multiple independent sources. Indicators are reliable enough to drive automated action.

Indicators

Observed patterns and artifacts associated with this entry. Each indicator can be copied into your detection stack or SIEM.

  • (?is)traceback[\s\S]{0,500}(?:GITHUB_TOKEN|GH_TOKEN|API_KEY)

Detection rule

A YARA-style pseudo-rule auto-generated from the indicators above. Useful as a starting point — adapt the syntax for your target detection platform.

YARA-style pseudo-rule
rule jiffy_ti_2026_000050
{
    meta:
        source = "jiffy-intel"
        severity = "high"
        description = "Auto-generated from Jiffy Intel indicators"
    strings:
    $content_pattern_0 = "(?is)traceback[\\s\\S]{0,500}(?:GITHUB_TOKEN|GH_TOKEN|API_KEY)"
    condition:
        $content_pattern_0
}

Auto-generated from the indicators above. Adapt syntax for your detection stack before deploying.

Affected tools

ToolVersionsStatus
Any MCP-capable agent*vulnerable

Example artifacts

Sanitized examples of artifacts Jiffy has observed exhibiting this pattern. Publisher handles are redacted; version ranges and status reflect the most recent scan.

  • gh-helpers-mcpMCP server
    Still live
    Source
    MCP Registry
    Versions
    1.0.0
    First observed
    Mar 3, 2026
  • repo-tools-mcpMCP server
    Under review
    Source
    MCP Registry
    Versions
    0.6.0
    First observed
    Mar 7, 2026

How to remediate

  1. 01Sanitize error payloads in MCP servers.
  2. 02Redact any env variable names matching secret patterns before returning errors.

Timeline & sources

Timeline

  1. First observedMar 3, 20261 month ago
  2. Last updatedApr 20, 2026today
  3. PublishedMar 15, 20261 month ago

Sources

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References

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