python-anyio — security advisory
AnyIO is a high level asynchronous concurrency and networking framework that works on top of either Trio or asyncio. Prior to 4.14.2, AnyIO starts process-pool workers with standard error connected to a pipe that the parent never drains, even though the documented behavior redirects all three standard streams. Worker code that writes enough attacker-influenced data to sys.stderr can fill the pipe and block before returning the standard-output protocol response, causing the awaiting process-pool call to remain blocked indefinitely. Applications that run untrusted or faulty worker code capable of producing substantial standard-error output are affected. This issue is fixed in version 4.14.2.
- Products
- python-anyio
- Affected versions
- 2.0.2-2, 3.5.0-2ubuntu1, 3.5.0-3ubuntu2, 3.7.0-1, 4.11.0-2, 4.11.0-3, 4.12.1-2, 4.12.1-3, 4.15.1-3, 4.2.0-1, 4.8.0-3
- Fixed versions
- Not specified
- CVEs
- CVE-2026-64847
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 03:12 UTC · Revision 1
Source evidence
AnyIO is a high level asynchronous concurrency and networking framework that works on top of either Trio or asyncio. Prior to 4.14.2, AnyIO starts process-pool workers with standard error connected to a pipe that the parent never drains, even though the documented behavior redirects all three standard streams. Worker code that writes enough attacker-influenced data to sys.stderr can fill the pipe and block before returning the standard-output protocol response, causing the awaiting process-pool call to remain blocked indefinitely. Applications that run untrusted or faulty worker code capable of producing substantial standard-error output are affected. This issue is fixed in version 4.14.2.
osv:UBUNTU-CVE-2026-64847
python-anyio
Fixed versions: Not specified
python-anyio
Fixed versions: Not specified
python-anyio
Fixed versions: Not specified
python-anyio
Fixed versions: Not specified
Complete source record
{
"id": "e1b365ee3f8c24bed4dd915d86395e2c9f9d76ce8fc4570f17bfc4d29a56a3ed",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-64847",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-64847",
"summary": "AnyIO is a high level asynchronous concurrency and networking framework that works on top of either Trio or asyncio. Prior to 4.14.2, AnyIO starts process-pool workers with standard error connected to a pipe that the parent never drains, even though the documented behavior redirects all three standard streams. Worker code that writes enough attacker-influenced data to sys.stderr can fill the pipe and block before returning the standard-output protocol response, causing the awaiting process-pool call to remain blocked indefinitely. Applications that run untrusted or faulty worker code capable of producing substantial standard-error output are affected. This issue is fixed in version 4.14.2.",
"evidence": "osv:UBUNTU-CVE-2026-64847",
"products": [
{
"name": {
"value": "python-anyio",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "2.0.2-2",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.0-2ubuntu1",
"evidence": "/affected/0/versions"
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{
"value": "3.5.0-3ubuntu2",
"evidence": "/affected/0/versions"
}
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{
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{
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{
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{
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"affected_versions": [
{
"value": "4.11.0-3",
"evidence": "/affected/2/versions"
},
{
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"evidence": "/affected/2/versions"
},
{
"value": "4.12.1-3",
"evidence": "/affected/2/versions"
},
{
"value": "4.15.1-3",
"evidence": "/affected/2/versions"
}
]
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{
"name": {
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"evidence": "/affected/3/package/name"
},
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"fixed_versions": [],
"affected_versions": [
{
"value": "4.8.0-3",
"evidence": "/affected/3/versions"
},
{
"value": "4.11.0-2",
"evidence": "/affected/3/versions"
},
{
"value": "4.11.0-3",
"evidence": "/affected/3/versions"
}
]
}
],
"severity": "medium",
"structured": {
"id": "UBUNTU-CVE-2026-64847",
"aliases": [
"UBUNTU-CVE-2026-64847"
],
"metrics": [
{
"type": "CVSS_V4",
"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": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
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"events": [
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"package": {
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"ecosystem": "Ubuntu:22.04:LTS"
},
"versions": [
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"3.5.0-2ubuntu1",
"3.5.0-3ubuntu2"
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"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-64847.json"
},
"ecosystem_specific": {
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{
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{
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"package": {
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"ecosystem": "Ubuntu:24.04:LTS"
},
"versions": [
"3.7.0-1",
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"database_specific": {
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"ecosystem": "Ubuntu:26.10"
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"versions": [
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"4.12.1-2",
"4.12.1-3",
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"database_specific": {
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"ecosystem_specific": {
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{
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"package": {
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"purl": "pkg:deb/ubuntu/python-anyio?arch=source&distro=resolute",
"ecosystem": "Ubuntu:26.04:LTS"
},
"versions": [
"4.8.0-3",
"4.11.0-2",
"4.11.0-3"
],
"database_specific": {
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},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-anyio",
"binary_version": "4.11.0-3"
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]
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}
],
"modified": "2026-10-17T13:00:33.675139976Z",
"provider": "osv",
"upstream": [
"CVE-2026-64847"
],
"references": [
"https://ubuntu.com/security/CVE-2026-64847",
"https://www.cve.org/CVERecord?id=CVE-2026-64847",
"https://github.com/agronholm/anyio/security/advisories/GHSA-5p39-cfhj-2xmp",
"https://github.com/agronholm/anyio/pull/1207",
"https://github.com/agronholm/anyio/commit/f1b7301c8264b0d2e8d24a5788fd29e93dea4040",
"https://github.com/agronholm/anyio/releases/tag/4.14.2"
]
},
"related_cves": [
{
"value": "CVE-2026-64847",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 360691,
"published_at": "2026-09-18T18:17:00+00:00"
}