BREW-MCP-ATLASSIAN-CVE-2… (GHSA-5P39-CFHJ-2XMP)
Vulnerability from osv_homebrew – Published: 2026-09-19 10:34 – Updated: 2026-11-10 09:50 – Source websiteImpact
AnyIO starts process-pool workers with stderr connected to a pipe but never drains that pipe. The worker redirects stdin and stdout to /dev/null to protect its protocol, but does not redirect stderr even though the documentation says all three standard streams are redirected. Worker code that writes enough attacker-influenced data to stderr can fill the pipe, block before returning the stdout protocol response, and wedge the awaiting process-pool call.
Anyone who runs untrusted or faulty code that writes too much to stderr is at risk.
Patches
This vulnerability will be patched in v4.14.2.
Workarounds
Closing sys.stderr in the target function should at least prevent the deadlock.
{
"affected": [
{
"ecosystem_specific": {
"fix": "bump",
"range_state": "fixed",
"resource": "anyio",
"resource_purl": "pkg:pypi/anyio@4.16.0",
"upstream_fixed_in": "4.14.2"
},
"package": {
"ecosystem": "Homebrew",
"name": "mcp-atlassian",
"purl": "pkg:brew/mcp-atlassian"
},
"ranges": [
{
"events": [
{
"introduced": "0.11.9"
},
{
"fixed": "0.23.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"database_specific": {
"confidence": "high",
"source": "matched",
"strategy": "registry",
"upstream_evidence": [
{
"ecosystem": "PyPI",
"key": "pkg:pypi/anyio@4.16.0",
"name": "anyio",
"resource": "anyio",
"strategy": "registry",
"subject_version": "4.16.0"
}
]
},
"details": "### Impact\nAnyIO starts process-pool workers with stderr connected to a pipe but never drains that pipe. The worker redirects stdin and stdout to /dev/null to protect its protocol, but does not redirect stderr even though the documentation says all three standard streams are redirected. Worker code that writes enough attacker-influenced data to stderr can fill the pipe, block before returning the stdout protocol response, and wedge the awaiting process-pool call.\n\nAnyone who runs untrusted or faulty code that writes too much to `stderr` is at risk.\n\n### Patches\nThis vulnerability will be patched in v4.14.2.\n\n### Workarounds\nClosing `sys.stderr` in the target function should at least prevent the deadlock.",
"id": "BREW-mcp-atlassian-CVE-2026-64847",
"modified": "2026-11-10T09:50:35Z",
"published": "2026-09-19T10:34:04Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/agronholm/anyio/security/advisories/GHSA-5p39-cfhj-2xmp"
},
{
"type": "WEB",
"url": "https://github.com/agronholm/anyio/pull/1207"
},
{
"type": "WEB",
"url": "https://github.com/agronholm/anyio/commit/f1b7301c8264b0d2e8d24a5788fd29e93dea4040"
},
{
"type": "PACKAGE",
"url": "https://github.com/agronholm/anyio"
},
{
"type": "WEB",
"url": "https://github.com/agronholm/anyio/releases/tag/4.14.2"
}
],
"schema_version": "1.7.3",
"severity": [
{
"score": "CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "AnyIO process-pool workers can block indefinitely on undrained stderr",
"upstream": [
"GHSA-5p39-cfhj-2xmp",
"CVE-2026-64847",
"PYSEC-2026-4024"
]
}
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| Author | Source | Type | Date | Other |
|---|
Nomenclature
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Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
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Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
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