CVE-2026-63349
HighCVSS 7.0Exploitation Probability (EPSS)
Low risk1th percentile - higher than 1% of all known CVEs
Summary
In AnyIO 4.14.0, open_process() forwards the group argument to the backend instead of extra_groups, despite accepting the extra_groups parameter. A call with extra_groups=[] to clear inherited supplementary groups can launch a child process that retains the parent's groups, weakening a privilege-dropping boundary. This affects POSIX applications using AnyIO subprocess helpers and is fixed in version 4.14.2.
Risk Assessment
A child process may retain the parent's group privileges, potentially enabling privilege escalation or access to resources that should be restricted. This impacts applications relying on AnyIO to launch less-privileged processes.
Recommendation
Upgrade AnyIO to version 4.14.2 or later. Review applications using extra_groups in AnyIO to ensure they do not depend on the flawed behavior.
Other vulnerabilities in AnyIO
See all- CVE-2026-63374Critical
AnyIO is a high level asynchronous concurrency and networking framework that works on top of either Trio or asyncio. Prior to 4.14.2, connect_tcp() and TLSStream.wrap() can validate internationalized host names after the standard library converts them with IDNA 2003 instead of IDNA 2008. When a connection to a non-ASCII domain is hijacked or redirected, an attacker can obtain a legitimate certificate for the different ASCII hostname produced by IDNA 2003 and present it to the client, causing the malicious endpoint's certificate to validate.
- CVE-2026-64847Medium
In AnyIO prior to 4.14.2, process-pool workers were started with stderr connected to a pipe the parent never drained. Worker code writing enough data to sys.stderr could fill the pipe and block before returning the response, causing the awaiting process-pool call to remain blocked indefinitely.
Original NVD description (English source)
AnyIO is a high level asynchronous concurrency and networking framework that works on top of either Trio or asyncio. In 4.14.0, AnyIO accepts the POSIX extra_groups argument in anyio.run_process() and anyio.open_process(), but open_process() forwards the group argument to the backend instead of extra_groups. A caller that supplies extra_groups=[] to clear inherited supplementary groups can therefore launch a child that retains the parent process groups, undermining a privilege-dropping boundary. If group is also supplied, the integer group value is passed where an iterable of supplementary groups is expected and the launch can fail with TypeError. This issue affects POSIX applications that rely on AnyIO subprocess helpers to launch less-privileged child processes. This issue is fixed in version 4.14.2.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS