CVE-2025-39758

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Source
https://cve.org/CVERecord?id=CVE-2025-39758
Import Source
https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-39758.json
JSON Data
https://api.test.osv.dev/v1/vulns/CVE-2025-39758
Downstream
Related
Published
2025-09-11T16:52:27Z
Modified
2026-08-25T03:30:30Z
Severity
  • 9.8 (Critical) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H CVSS Calculator
Summary
RDMA/siw: Fix the sendmsg byte count in siw_tcp_sendpages
Details

In the Linux kernel, the following vulnerability has been resolved:

RDMA/siw: Fix the sendmsg byte count in siw_tcp_sendpages

Ever since commit c2ff29e99a76 ("siw: Inline do_tcp_sendpages()"), we have been doing this:

static int siw_tcp_sendpages(struct socket *s, struct page *page, int offset, size_t size) [...] / Calculate the number of bytes we need to push, for this page * specifically / size_t bytes = min_t(size_t, PAGE_SIZE - offset, size); / If we can't splice it, then copy it in, as normal / if (!sendpage_ok(page[i])) msg.msg_flags &= ~MSG_SPLICE_PAGES; / Set the bvec pointing to the page, with len $bytes / bvec_set_page(&bvec, page[i], bytes, offset); / Set the iter to $size, aka the size of the whole sendpages (!!!) / iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size); try_page_again: lock_sock(sk); / Sendmsg with $size size (!!!) */ rv = tcp_sendmsg_locked(sk, &msg, size);

This means we've been sending oversized iov_iters and tcp_sendmsg calls for a while. This has a been a benign bug because sendpage_ok() always returned true. With the recent slab allocator changes being slowly introduced into next (that disallow sendpage on large kmalloc allocations), we have recently hit out-of-bounds crashes, due to slight differences in iov_iter behavior between the MSG_SPLICE_PAGES and "regular" copy paths:

(MSG_SPLICE_PAGES) skb_splice_from_iter iov_iter_extract_pages iov_iter_extract_bvec_pages uses i->nr_segs to correctly stop in its tracks before OoB'ing everywhere skb_splice_from_iter gets a "short" read

(!MSG_SPLICE_PAGES) skb_copy_to_page_nocache copy=iov_iter_count [...] copy_from_iter /* this doesn't help */ if (unlikely(iter->count < len)) len = iter->count; iterate_bvec ... and we run off the bvecs

Fix this by properly setting the iov_iter's byte count, plus sending the correct byte count to tcp_sendmsg_locked.

Database specific 
{
    "cna_assigner":  "Linux",
    "osv_generated_from":  "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39758.json"
}
References

Affected packages

Git / git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

Affected ranges

Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
a19a58ab12695abb91a4e8ecf62cc0bc5badefbe
Fixed
b47c4b7cb78b6382c6d1af0bfc0d8218e4f445cc
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
c2ff29e99a764769eb2ce3a1a5585013633ee9a6
Fixed
5661fdd218c2799001b88c17acd19f4395e4488e
Fixed
673cf582fd788af12cdacfb62a6a593083542481
Fixed
42ebc16d9d2563f1a1ce0f05b643ee68d54fabf8
Fixed
edf82bc8150570167a33a7d54627d66614cbf841
Fixed
c18646248fed07683d4cee8a8af933fc4fe83c0d

Database specific

source 
"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-39758.json"

Linux / Kernel

Package

Name
Kernel

Affected ranges

Type
ECOSYSTEM
Events
Introduced
6.5.0
Fixed
6.6.103
Type
ECOSYSTEM
Events
Introduced
6.7.0
Fixed
6.12.43
Type
ECOSYSTEM
Events
Introduced
6.13.0
Fixed
6.15.11
Type
ECOSYSTEM
Events
Introduced
6.16.0
Fixed
6.16.2

Database specific

source 
"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-39758.json"