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CVE-2024-26921— inet: inet_defrag: prevent sk release while still in use

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inet inet_defrag中存在释放后重用漏洞。

CVSS 7.8 · High EPSS 0.40% · P32

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 16

VendorProduct Version RangeStatus
Linux Linux 7026b1ddb6b8d4e6ee33dc2bd06c0ca8746fa7ab< 1b6de5e6575b56502665c65cf93b0ae6aa0f51ab affected
7026b1ddb6b8d4e6ee33dc2bd06c0ca8746fa7ab< 9705f447bf9a6cd088300ad2c407b5e1c6591091 affected
7026b1ddb6b8d4e6ee33dc2bd06c0ca8746fa7ab< 4318608dc28ef184158b4045896740716bea23f0 affected
7026b1ddb6b8d4e6ee33dc2bd06c0ca8746fa7ab< 7d0567842b78390dd9b60f00f1d8f838d540e325 affected
7026b1ddb6b8d4e6ee33dc2bd06c0ca8746fa7ab< f4877225313d474659ee53150ccc3d553a978727 affected
7026b1ddb6b8d4e6ee33dc2bd06c0ca8746fa7ab< e09cbe017311508c21e0739e97198a8388b98981 affected
7026b1ddb6b8d4e6ee33dc2bd06c0ca8746fa7ab< 18685451fc4e546fc0e718580d32df3c0e5c8272 affected
4.1 affected
… +8 more rows
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I. Basic Information for CVE-2024-26921

Vulnerability Information
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Vulnerability Title
inet: inet_defrag: prevent sk release while still in use
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: inet: inet_defrag: prevent sk release while still in use ip_local_out() and other functions can pass skb->sk as function argument. If the skb is a fragment and reassembly happens before such function call returns, the sk must not be released. This affects skb fragments reassembled via netfilter or similar modules, e.g. openvswitch or ct_act.c, when run as part of tx pipeline. Eric Dumazet made an initial analysis of this bug. Quoting Eric: Calling ip_defrag() in output path is also implying skb_orphan(), which is buggy because output path relies on sk not disappearing. A relevant old patch about the issue was : 8282f27449bf ("inet: frag: Always orphan skbs inside ip_defrag()") [..] net/ipv4/ip_output.c depends on skb->sk being set, and probably to an inet socket, not an arbitrary one. If we orphan the packet in ipvlan, then downstream things like FQ packet scheduler will not work properly. We need to change ip_defrag() to only use skb_orphan() when really needed, ie whenever frag_list is going to be used. Eric suggested to stash sk in fragment queue and made an initial patch. However there is a problem with this: If skb is refragmented again right after, ip_do_fragment() will copy head->sk to the new fragments, and sets up destructor to sock_wfree. IOW, we have no choice but to fix up sk_wmem accouting to reflect the fully reassembled skb, else wmem will underflow. This change moves the orphan down into the core, to last possible moment. As ip_defrag_offset is aliased with sk_buff->sk member, we must move the offset into the FRAG_CB, else skb->sk gets clobbered. This allows to delay the orphaning long enough to learn if the skb has to be queued or if the skb is completing the reasm queue. In the former case, things work as before, skb is orphaned. This is safe because skb gets queued/stolen and won't continue past reasm engine. In the latter case, we will steal the skb->sk reference, reattach it to the head skb, and fix up wmem accouting when inet_frag inflates truesize.
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inet inet_defrag中存在释放后重用漏洞。
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 7026b1ddb6b8d4e6ee33dc2bd06c0ca8746fa7ab ~ 1b6de5e6575b56502665c65cf93b0ae6aa0f51ab -
Linux Linux 4.1 -

II. Public POCs for CVE-2024-26921

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III. Intelligence Information for CVE-2024-26921

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Patches & Fixes for CVE-2024-26921 (1)

Other References for CVE-2024-26921 (6)

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2024-26921

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