CVE-2025-39758

MEDIUM EPSS 4.1%
Published Sep 11, 20259mo ago · Modified Jun 17, 20261w ago
5.5 CVSS 3.1
Medium
Find Similar
Published Sep 11, 2025 9mo ago
Last Modified Jun 17, 2026 1w ago

Description

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.

CVSS Details

Base Score
5.5
Exploitability
1.8
Impact
3.6
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack Vector Local
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality None
Integrity None
Availability High

Threat Intelligence

EPSS Exploit Probability
4.1% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Affected Products 4

VendorProductVersionRange
linuxlinux_kernel*≥6.5  –  <6.6.103
linuxlinux_kernel*≥6.7  –  <6.12.43
linuxlinux_kernel*≥6.13  –  <6.15.11
linuxlinux_kernel*≥6.16  –  <6.16.2

References 5

  • git.kernel.org https://git.kernel.org/stable/c/42ebc16d9d2563f1a1ce0f05b643ee68d54fabf8
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/5661fdd218c2799001b88c17acd19f4395e4488e
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/673cf582fd788af12cdacfb62a6a593083542481
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/c18646248fed07683d4cee8a8af933fc4fe83c0d
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/edf82bc8150570167a33a7d54627d66614cbf841
    Patch

Remediation

  • git.kernel.org https://git.kernel.org/stable/c/42ebc16d9d2563f1a1ce0f05b643ee68d54fabf8
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/5661fdd218c2799001b88c17acd19f4395e4488e
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/673cf582fd788af12cdacfb62a6a593083542481
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/c18646248fed07683d4cee8a8af933fc4fe83c0d
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/edf82bc8150570167a33a7d54627d66614cbf841
    Patch