GHSA-7C5H-C675-2HVR
Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-17 06:33In the Linux kernel, the following vulnerability has been resolved:
xprtrdma: Fix bcall rep leak and unbounded peek
rpcrdma_is_bcall() decodes a reply's first words to decide whether the frame is a backchannel call. Two issues in that decode path let a short or malformed reply leak the receive buffer and drain the Receive queue.
First, the speculative peek
p = xdr_inline_decode(xdr, 0);
/* five p++ reads follow */
asks xdr_inline_decode() for zero bytes, which returns xdr->p without consulting xdr->end. The five subsequent __be32 reads can then walk up to 20 bytes past the wire payload into stale regbuf contents and misclassify the reply as a backchannel call.
Second, after the post-peek
p = xdr_inline_decode(xdr, 3 * sizeof(*p));
if (unlikely(!p))
return true;
the short-header arm returns true without calling rpcrdma_bc_receive_call(). The contract with the caller is that a true return transfers ownership of rep to the backchannel path:
rpcrdma_reply_handler()
if (rpcrdma_is_bcall(r_xprt, rep))
return; /* bare return, skips out_post */
...
out_post:
rpcrdma_post_recvs(r_xprt, credits + ...);
Because rpcrdma_bc_receive_call() never ran, no one took rep, but rpcrdma_reply_handler still bare-returns past rpcrdma_rep_put() and rpcrdma_post_recvs(). The rep, with its persistently DMA-mapped receive buffer, is orphaned on rb_all_reps and freed only at transport teardown. This completion reposts nothing, so its slot is reclaimed only when a later forward-channel reply reaches out_post and rpcrdma_post_recvs() allocates a fresh rep to backfill; absent that traffic the Receive queue drains and the peer's Sends draw RNR NAKs.
Fix by consulting xdr->end after the zero-length peek so the five __be32 reads cannot run unless 20 bytes of wire payload remain. A byte-precise comparison against xdr->end is required because a non-4-aligned receive rounds the stream's word count up past the true payload. Also return false from the short-header arm so the reply falls through the normal out_norqst cleanup chain (rpcrdma_rep_put() plus rpcrdma_post_recvs()).
{
"affected": [],
"aliases": [
"CVE-2026-72466"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T06:22:20Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nxprtrdma: Fix bcall rep leak and unbounded peek\n\nrpcrdma_is_bcall() decodes a reply\u0027s first words to decide whether\nthe frame is a backchannel call. Two issues in that decode path\nlet a short or malformed reply leak the receive buffer and drain\nthe Receive queue.\n\nFirst, the speculative peek\n\n p = xdr_inline_decode(xdr, 0);\n /* five p++ reads follow */\n\nasks xdr_inline_decode() for zero bytes, which returns xdr-\u003ep\nwithout consulting xdr-\u003eend. The five subsequent __be32 reads can\nthen walk up to 20 bytes past the wire payload into stale regbuf\ncontents and misclassify the reply as a backchannel call.\n\nSecond, after the post-peek\n\n p = xdr_inline_decode(xdr, 3 * sizeof(*p));\n if (unlikely(!p))\n return true;\n\nthe short-header arm returns true without calling\nrpcrdma_bc_receive_call(). The contract with the caller is that a\ntrue return transfers ownership of rep to the backchannel path:\n\n rpcrdma_reply_handler()\n if (rpcrdma_is_bcall(r_xprt, rep))\n return; /* bare return, skips out_post */\n ...\n out_post:\n rpcrdma_post_recvs(r_xprt, credits + ...);\n\nBecause rpcrdma_bc_receive_call() never ran, no one took rep, but\nrpcrdma_reply_handler still bare-returns past rpcrdma_rep_put()\nand rpcrdma_post_recvs(). The rep, with its persistently\nDMA-mapped receive buffer, is orphaned on rb_all_reps and freed\nonly at transport teardown. This completion reposts nothing, so\nits slot is reclaimed only when a later forward-channel reply\nreaches out_post and rpcrdma_post_recvs() allocates a fresh rep to\nbackfill; absent that traffic the Receive queue drains and the\npeer\u0027s Sends draw RNR NAKs.\n\nFix by consulting xdr-\u003eend after the zero-length peek so the five\n__be32 reads cannot run unless 20 bytes of wire payload remain. A\nbyte-precise comparison against xdr-\u003eend is required because a\nnon-4-aligned receive rounds the stream\u0027s word count up past the\ntrue payload. Also return false from the short-header arm so the\nreply falls through the normal out_norqst cleanup chain\n(rpcrdma_rep_put() plus rpcrdma_post_recvs()).",
"id": "GHSA-7c5h-c675-2hvr",
"modified": "2026-08-17T06:33:31Z",
"published": "2026-08-15T06:32:25Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-72466"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/07aa506436be7634e381e1e1f6d0efa9efc81ecc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0cee8f9c3b14bd6dee9c4310090a7f45b89b834f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/118a16a18c59f7ad8084b2d13988839b669fca10"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7afc2f8d2fd9394724df9eaf22ce7a71029a5fba"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/88b5346284a184a6b7d019912232a571d672d3e3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c7653d5cebc8492c77ec0415b5e9c0fb3e644bc6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d7a2870dde3bb09d51d6b9c877642996ad6b92dd"
}
],
"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"
}
]
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.