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CVE-2024-26923— af_unix: Fix garbage collector racing against connect()

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于垃圾收集器与connect函数之前存在竞争。

CVSS 7.8 · High EPSS 0.21% · P10

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9< a36ae0ec2353015f0f6762e59f4c2dbc0c906423 affected
1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9< 343c5372d5e17b306db5f8f3c895539b06e3177f affected
1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9< 2e2a03787f4f0abc0072350654ab0ef3324d9db3 affected
1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9< e76c2678228f6aec74b305ae30c9374cc2f28a51 affected
1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9< b75722be422c276b699200de90527d01c602ea7c affected
1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9< 507cc232ffe53a352847893f8177d276c3b532a9 affected
1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9< dbdf7bec5c920200077d693193f989cb1513f009 affected
1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9< 47d8ac011fe1c9251070e1bd64cb10b48193ec51 affected
… +10 more rows
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I. Basic Information for CVE-2024-26923

Vulnerability Information
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Vulnerability Title
af_unix: Fix garbage collector racing against connect()
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于垃圾收集器与connect函数之前存在竞争。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 ~ a36ae0ec2353015f0f6762e59f4c2dbc0c906423 -
Linux Linux 2.6.23 -

II. Public POCs for CVE-2024-26923

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III. Intelligence Information for CVE-2024-26923

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Mailing List Discussions for CVE-2024-26923 (2)

Other References for CVE-2024-26923 (7)

Same Patch Batch · Linux · 2024-04-24 · 4 CVEs total

CVE-2024-26926 7.8 HIGH binder: check offset alignment in binder_get_object()
CVE-2024-26925 7.8 HIGH netfilter: nf_tables: release mutex after nft_gc_seq_end from abort path
CVE-2024-26924 7.8 HIGH netfilter: nft_set_pipapo: do not free live element

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2024-26923

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