CVE-2026-63349

Privilege retention via misrouted supplementary-group argument

Published Sep 18, 2026 · Updated Sep 18, 2026

Privilege retention in AnyIO 4.14.0 through 4.14.1 allows local users to preserve supplementary groups in spawned child processes. The open_process function assigns group rather than extra_groups to the backend keyword argument, so run_process and open_process cannot clear or set the child's supplementary groups. Exploitation requires a POSIX application to use these helpers as a privilege boundary; the child retains access granted to the parent's supplementary groups.

CVSS severity7.0
High
EPSS probability0.11%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Privilege retention in AnyIO 4.14.0 through 4.14.1 allows local users to preserve supplementary groups in spawned child processes. The open_process function assigns group rather than extra_groups to the backend keyword argument, so run_process and open_process cannot clear or set the child's supplementary groups. Exploitation requires a POSIX application to use these helpers as a privilege boundary; the child retains access granted to the parent's supplementary groups.

The record

CVE
CVE-2026-63349
Published
Sep 18, 2026
Updated
Sep 18, 2026
Vendor
Alex Grönholm
Product
AnyIO
Classifications
CWE-266, CWE-269, T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Sep 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 4.14.0, < 4.14.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Alex Grönholm · AnyIOversion=>= 4.14.0, < 4.14.2

Published CVSS scores

7.0GitHub Security AdvisoryCVSS:4.0/AV:L/AC:H/AT:P/PR:H/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-266Incorrect Privilege Assignment
CWE-269Improper Privilege Management
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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