CVE-2026-72466: xprtrdma: Fix bcall rep leak and unbounded peek
In the Linux kernel, the following vulnerability has been resolved:
xprtrdma: Fix bcall rep leak and unbounded peek
rpcrdmaisbcall() 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 = xdrinlinedecode(xdr, 0); / five p++ reads follow /
asks xdrinlinedecode() 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 = xdrinlinedecode(xdr, 3 sizeof(p)); if (unlikely(!p)) return true;
the short-header arm returns true without calling rpcrdmabcreceivecall(). The contract with the caller is that a true return transfers ownership of rep to the backchannel path:
rpcrdmareplyhandler() if (rpcrdmaisbcall(rxprt, rep)) return; / bare return, skips outpost / ... outpost: rpcrdmapostrecvs(rxprt, credits + ...);
Because rpcrdmabcreceivecall() never ran, no one took rep, but rpcrdmareplyhandler still bare-returns past rpcrdmarepput() and rpcrdmapostrecvs(). The rep, with its persistently DMA-mapped receive buffer, is orphaned on rballreps and freed only at transport teardown. This completion reposts nothing, so its slot is reclaimed only when a later forward-channel reply reaches outpost and rpcrdmapostrecvs() 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 outnorqst cleanup chain (rpcrdmarepput() plus rpcrdmapostrecvs()).
Affected Software
Remediation
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In Linux kernel xprtrdma, update rpcrdma_is_bcall() to consult xdr->end after the zero-length xdr_inline_decode(xdr, 0) peek so the five subsequent __be32 reads occur only when 20 bytes of wire payload remain; use a byte-precise comparison. Also make the short-header arm return false so processing follows the normal out_norqst cleanup chain, including rpcrdma_rep_put() and rpcrdma_post_recvs().
Event History
Frequently Asked Questions
What is the severity of CVE-2026-72466?
The severity of CVE-2026-72466 is rated at 37.
How do I fix CVE-2026-72466?
To fix CVE-2026-72466, ensure your Linux kernel is updated to the latest version where the vulnerability has been addressed.
What are the potential impacts of CVE-2026-72466?
CVE-2026-72466 can lead to information leakage from the receive buffer due to issues in the decoding path.
Which software is affected by CVE-2026-72466?
CVE-2026-72466 affects the Linux kernel, specifically related to xprtrdma.
When was CVE-2026-72466 published?
CVE-2026-72466 was published on August 15, 2026.