Bug 2537927 (CVE-2026-63349)

Summary: CVE-2026-63349 anyio: AnyIO: Privilege retention in child processes due to incorrect group handling
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: alinfoot, anpicker, anthomas, aprice, bbrownin, blitton, dfreiber, dkeler, doconnor, drow, dschmidt, dtrifiro, dymurray, ebourniv, eglynn, ehelms, gbenhaim, ggainey, hasun, ibolton, ilpinto, jburrell, jdobes, jfula, jjoyce, jlanda, jmatthew, jmitchel, jmontleo, jowilson, jpasqual, jpretori, jsamir, jschluet, juwatts, jwong, kaycoth, kgaikwad, kshier, lhh, ltomasbo, mbarnett, mburns, mdellweg, mgarciac, mhayden, mhulan, niyer, nmoumoul, nyancey, oezr, omaciel, ometelka, orabin, osousa, pcreech, pgaikwad, prwatson, ptisnovs, rbobbitt, rchan, rekumar, rjohnson, sbunciak, sdoran, simaishi, slucidi, smallamp, sseago, stcannon, suppawar, syedriko, thason, tmalecek, twaugh, vkumar, vvoronko, weaton, xdharmai, yguenane, ykashtan
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in AnyIO. When launching child processes using `anyio.open_process()`, the `extra_groups` argument is incorrectly handled. This can allow a less-privileged child process to retain the supplementary groups of its parent, potentially leading to unintended privilege retention. This issue affects POSIX applications that rely on AnyIO to manage subprocesses with reduced privileges.
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Description OSIDB Bzimport 2026-09-22 16:05:56 UTC 
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.