CVE-2024-27415

Published May 17, 2024

Last updated 9 months ago

CVSS medium 4.7

Overview

Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: bridge: confirm multicast packets before passing them up the stack conntrack nf_confirm logic cannot handle cloned skbs referencing the same nf_conn entry, which will happen for multicast (broadcast) frames on bridges. Example: macvlan0 | br0 / \ ethX ethY ethX (or Y) receives a L2 multicast or broadcast packet containing an IP packet, flow is not yet in conntrack table. 1. skb passes through bridge and fake-ip (br_netfilter)Prerouting. -> skb->_nfct now references a unconfirmed entry 2. skb is broad/mcast packet. bridge now passes clones out on each bridge interface. 3. skb gets passed up the stack. 4. In macvlan case, macvlan driver retains clone(s) of the mcast skb and schedules a work queue to send them out on the lower devices. The clone skb->_nfct is not a copy, it is the same entry as the original skb. The macvlan rx handler then returns RX_HANDLER_PASS. 5. Normal conntrack hooks (in NF_INET_LOCAL_IN) confirm the orig skb. The Macvlan broadcast worker and normal confirm path will race. This race will not happen if step 2 already confirmed a clone. In that case later steps perform skb_clone() with skb->_nfct already confirmed (in hash table). This works fine. But such confirmation won't happen when eb/ip/nftables rules dropped the packets before they reached the nf_confirm step in postrouting. Pablo points out that nf_conntrack_bridge doesn't allow use of stateful nat, so we can safely discard the nf_conn entry and let inet call conntrack again. This doesn't work for bridge netfilter: skb could have a nat transformation. Also bridge nf prevents re-invocation of inet prerouting via 'sabotage_in' hook. Work around this problem by explicit confirmation of the entry at LOCAL_IN time, before upper layer has a chance to clone the unconfirmed entry. The downside is that this disables NAT and conntrack helpers. Alternative fix would be to add locking to all code parts that deal with unconfirmed packets, but even if that could be done in a sane way this opens up other problems, for example: -m physdev --physdev-out eth0 -j SNAT --snat-to 1.2.3.4 -m physdev --physdev-out eth1 -j SNAT --snat-to 1.2.3.5 For multicast case, only one of such conflicting mappings will be created, conntrack only handles 1:1 NAT mappings. Users should set create a setup that explicitly marks such traffic NOTRACK (conntrack bypass) to avoid this, but we cannot auto-bypass them, ruleset might have accept rules for untracked traffic already, so user-visible behaviour would change.
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Analyzed
Products
linux_kernel

Risk scores

CVSS 3.1

Type
Primary
Base score
4.7
Impact score
3.6
Exploitability score
1
Vector string
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Severity
MEDIUM

Weaknesses

nvd@nist.gov
CWE-362

Social media

Hype score
Not currently trending

Configurations

Related CVEs

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  3. In the Linux kernel, the following vulnerability has been resolved: wifi: ath12k: do WoW offloads only on primary link In case of multi-link connection, WCN7850 firmware crashes due to WoW offloads enabled on both primary and secondary links. Change to do it only on primary link to fix it. Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.1.c5-00284-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1•CVE-2026-46271
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  5. In the Linux kernel, the following vulnerability has been resolved: pinctrl: canaan: k230: Fix NULL pointer dereference when parsing devicetree When probing the k230 pinctrl driver, the kernel triggers a NULL pointer dereference. The crash trace showed: [ 0.732084] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000068 [ 0.740737] ... [ 0.776296] epc : k230_pinctrl_probe+0x1be/0x4fc In k230_pinctrl_parse_functions(), we attempt to retrieve the device pointer via info->pctl_dev->dev, but info->pctl_dev is only initialized after k230_pinctrl_parse_dt() completes. At the time of DT parsing, info->pctl_dev is still NULL, leading to the invalid dereference of info->pctl_dev->dev. Use the already available device pointer from platform_device instead of accessing through uninitialized pctl_dev.•CVE-2026-46269

References

Sources include official advisories and independent security research.