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.
CVE-2026-64847
MEDIUMPre-NVD 6.86.8—Trending — 3 sources updated this week
EchelonGraph scoreMEDIUM confidence
This medium-severity CVE scores 6.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1%, top 98% 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
6.8EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.8Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 6.8
- EG Score
- 6.8(medium)
- EG Risk
- 31(Track)EG Risk 31/100SSVC: 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 computedSeverity68% × 45%Exploitation0% × 40%Automatability0% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 2%
- KEV
- Not listed
Published
September 18, 2026
Last Modified
September 18, 2026
Advisory Details (4)
Auto-updated Sep 18, 2026Patch available. Sources: github, github_pr, github_commit, github_release.
github_release Patch Available
4.14.2
Patch available: agronholm/anyio 4.14.2
https://github.com/agronholm/anyio/releases/tag/4.14.2github_commit Patch Available
commit f1b7301c8264 (agronholm/anyio)
Patch available: agronholm/anyio 4.14.2 (contains commit f1b7301c8264)
https://github.com/agronholm/anyio/commit/f1b7301c8264b0d2e8d24a5788fd29e93dea4040github_pr Patch Available
Fixed stderr writes in a worker subprocess causing a deadlock
Patch available: agronholm/anyio 4.14.2 (PR #1207 merged 2026-07-08)
https://github.com/agronholm/anyio/pull/1207github Patch Available
AnyIO process-pool workers can block indefinitely on undrained stderr · Advisory · agronholm/anyio · GitHub
Affected: v4.14.2.
https://github.com/agronholm/anyio/security/advisories/GHSA-5p39-cfhj-2xmpVendor Advisories for CVE-2026-64847(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 6× in last 7d / 6× 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.
- 2026-09-20 20:16 UTCEPSS rescore
- 2026-09-19 18:01 UTCEG score recompute
- 2026-09-18 18:27 UTCEG score recompute
- 2026-09-18 18:15 UTCEG score recompute
- 2026-09-18 17:19 UTCEG score recompute
- 2026-09-18 17:19 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Frequently asked(5)
What is CVE-2026-64847?
CVE-2026-64847 is a medium vulnerability published on September 18, 2026. 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…
When was CVE-2026-64847 disclosed?
CVE-2026-64847 was first published in the National Vulnerability Database on September 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-64847 actively exploited?
CVE-2026-64847 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 97.8% of all scored CVEs.
What is the CVSS score of CVE-2026-64847?
CVE-2026-64847 has a CVSS v3 base score of 6.8 (NVD).
How do I remediate CVE-2026-64847?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-64847, 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
Explore the affected products and dependency analysis for CVE-2026-64847
Is Your Infrastructure Affected by CVE-2026-64847?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.