CVE-2024-26923

af_unix: Fix garbage collector racing against connect()

Published Apr 24, 2024 CVSS 3.1 · 7.8 High EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

af_unix: Fix garbage collector racing against connect()

Garbage collector does not take into account the risk of embryo getting
enqueued during the garbage collection. If such embryo has a peer that
carries SCM_RIGHTS, two consecutive passes of scan_children() may see a
different set of children. Leading to an incorrectly elevated inflight
count, and then a dangling pointer within the gc_inflight_list.

sockets are AF_UNIX/SOCK_STREAM
S is an unconnected socket
L is a listening in-flight socket bound to addr, not in fdtable
V's fd will be passed via sendmsg(), gets inflight count bumped

connect(S, addr) sendmsg(S, [V]); close(V) __unix_gc()
---------------- ------------------------- -----------

NS = unix_create1()
skb1 = sock_wmalloc(NS)
L = unix_find_other(addr)
unix_state_lock(L)
unix_peer(S) = NS
// V count=1 inflight=0

NS = unix_peer(S)
skb2 = sock_alloc()
skb_queue_tail(NS, skb2[V])

// V became in-flight
// V count=2 inflight=1

close(V)

// V count=1 inflight=1
// GC candidate condition met

for u in gc_inflight_list:
if (total_refs == inflight_refs)
add u to gc_candidates

// gc_candidates={L, V}

for u in gc_candidates:
scan_children(u, dec_inflight)

// embryo (skb1) was not
// reachable from L yet, so V's
// inflight remains unchanged
__skb_queue_tail(L, skb1)
unix_state_unlock(L)
for u in gc_candidates:
if (u.inflight)
scan_children(u, inc_inflight_move_tail)

// V count=1 inflight=2 (!)

If there is a GC-candidate listening socket, lock/unlock its state. This
makes GC wait until the end of any ongoing connect() to that socket. After
flipping the lock, a possibly SCM-laden embryo is already enqueued. And if
there is another embryo coming, it can not possibly carry SCM_RIGHTS. At
this point, unix_inflight() can not happen because unix_gc_lock is already
taken. Inflight graph remains unaffected.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-3840-1 linux security update
Debian DLA Debian DLA DLA-3842-1 linux-5.10 security update
Debian DSA Debian DSA DSA-5680-1 linux security update
Debian DSA Debian DSA DSA-5681-1 linux security update
Ubuntu USN Ubuntu USN USN-6893-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6893-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6893-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6895-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6895-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6895-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6895-4 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6896-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6896-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6896-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6896-4 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6896-5 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6898-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6898-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6898-3 Linux kernel kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6898-4 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6900-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6917-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6918-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6919-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6926-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6926-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6926-3 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-6927-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6938-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7019-1 Linux kernel vulnerabilities
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 4.7, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H'}

cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
First Time appeared Debian
Debian debian Linux
Linux
Linux linux Kernel
CPEs cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.9:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.9:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.9:rc3:*:*:*:*:*:*
Vendors & Products Debian
Debian debian Linux
Linux
Linux linux Kernel
Metrics cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

cvssV3_1

{'score': 4.7, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H'}

Type Values Removed Values Added
Metrics epss

{'score': 0.00076}

epss

{'score': 0.00078}

Type Values Removed Values Added
CPEs cpe:/a:redhat:enterprise_linux:9
cpe:/o:redhat:enterprise_linux:9
Type Values Removed Values Added
First Time appeared Redhat rhel Aus
Redhat rhel E4s
Redhat rhel Tus
CPEs cpe:/o:redhat:rhel_aus:8.6
cpe:/o:redhat:rhel_e4s:8.6
cpe:/o:redhat:rhel_tus:8.6
Vendors & Products Redhat rhel Aus
Redhat rhel E4s
Redhat rhel Tus
Type Values Removed Values Added
CPEs cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:rhel_eus:8.8
Type Values Removed Values Added
First Time appeared Redhat enterprise Linux
CPEs cpe:/a:redhat:enterprise_linux:8::nfv
Vendors & Products Redhat enterprise Linux
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Nov 3, 2026, 9:52 PM
Reserved
Feb 19, 2024, 2:20 PM
Status
Modified
Published
Apr 25, 2024, 6:15 AM
Modified
Nov 3, 2026, 10:17 PM
Severity
Moderate
Public date
Apr 24, 2024, 12:00 AM