GHSA-C2X8-R5F6-55C5
Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-17 06:33In the Linux kernel, the following vulnerability has been resolved:
rxrpc: Don't move a peeked OOB message onto the pending queue
rxrpc_recvmsg_oob() takes a received oob message off recvmsg_oobq and, if a response is needed, moves it onto the pending_oobq tree. However, only the unlink from recvmsg_oobq is guarded by MSG_PEEK; the move onto pending_oobq always runs.
As a result, reading a challenge with MSG_PEEK leaves the skb on recvmsg_oobq while also adding it to pending_oobq. Since struct sk_buff's rbnode shares storage with its next and prev pointers, rb_insert_color() overwrites the list linkage, and the skb, which holds a single reference, becomes reachable from both queues at once.
When the socket is closed both queues are drained in turn. While draining recvmsg_oobq, __skb_unlink() follows the next and prev pointers that rbnode has overwritten and writes to a bad address. Also, as the skb holds a single reference but is freed from each queue, both the skb and the connection reference it holds are released twice. This leads to memory corruption and to a use-after-free caused by the connection refcount underflow.
MSG_PEEK does not consume the message from the queue, so only unlink it from recvmsg_oobq and then move it onto pending_oobq or free it when the message is actually consumed.
{
"affected": [],
"aliases": [
"CVE-2026-74434"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T06:22:45Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nrxrpc: Don\u0027t move a peeked OOB message onto the pending queue\n\nrxrpc_recvmsg_oob() takes a received oob message off recvmsg_oobq and,\nif a response is needed, moves it onto the pending_oobq tree. However,\nonly the unlink from recvmsg_oobq is guarded by MSG_PEEK; the move onto\npending_oobq always runs.\n\nAs a result, reading a challenge with MSG_PEEK leaves the skb on\nrecvmsg_oobq while also adding it to pending_oobq. Since struct\nsk_buff\u0027s rbnode shares storage with its next and prev pointers,\nrb_insert_color() overwrites the list linkage, and the skb, which holds\na single reference, becomes reachable from both queues at once.\n\nWhen the socket is closed both queues are drained in turn. While\ndraining recvmsg_oobq, __skb_unlink() follows the next and prev\npointers that rbnode has overwritten and writes to a bad address. Also,\nas the skb holds a single reference but is freed from each queue, both\nthe skb and the connection reference it holds are released twice. This\nleads to memory corruption and to a use-after-free caused by the\nconnection refcount underflow.\n\nMSG_PEEK does not consume the message from the queue, so only unlink it\nfrom recvmsg_oobq and then move it onto pending_oobq or free it when\nthe message is actually consumed.",
"id": "GHSA-c2x8-r5f6-55c5",
"modified": "2026-08-17T06:33:45Z",
"published": "2026-08-15T06:32:33Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74434"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5801cff7d5d7b4e9d877dfb627b23eb63167f02c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5f470cc883416fea6d3bce18ef96bf91dd49ffc3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9ada3931beb37068fcb725b34b0398457009f343"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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