Bug 2521497 (CVE-2026-74610)

Summary:	CVE-2026-74610 kernel: tls: don't leave a full plaintext sk_msg ring unpushed
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	rhel-process-autobot, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's Transport Layer Security (TLS) implementation. An unprivileged local user could trigger a kernel null pointer dereference by sending specific data on a loopback TCP socket with the TLS Upper Layer Protocol (ULP) attached. This vulnerability occurs because the TLS software send message function does not correctly handle a full plaintext message ring, leading to memory corruption and a system crash, resulting in a Denial of Service (DoS).	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-08-22 15:48:26 UTC

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

tls: don't leave a full plaintext sk_msg ring unpushed

When the copy path in tls_sw_sendmsg_locked() adds the fragment that fills
the plaintext sk_msg ring, it does not set full_record, so the record is
left full and unpushed.  A later splice() then adds to an already full
ring: sk_msg_page_add() has no fullness check of its own, so sg.end wraps
onto sg.start and the ring appears empty.  Fragments added after that
overwrite live entries, and sg.size no longer matches what is reachable
between sg.start and sg.end, so pushing the record runs the scatterwalk off
the end of the scatterlist.

An unprivileged user can trigger this on a loopback TCP socket with the
"tls" ULP attached:

  BUG: kernel NULL pointer dereference, address: 0000000000000008
  RIP: 0010:memcpy_from_scatterwalk+0x32/0xc0
  Call Trace:
   skcipher_walk_next+0x1d1/0x2c0
   gcm_encrypt_aesni_avx+0x1e9/0x220
   bpf_exec_tx_verdict+0x3bb/0x860
   tls_sw_sendmsg+0xa1a/0xca0
   __sys_sendto+0x1da/0x1f0

Set full_record in the copy path when the ring becomes full, and push a
record that is already full on entry to the sendmsg loop.

Comment 1 gkamathe 2026-08-24 13:20:05 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026082217-CVE-2026-74610-3bed@gregkh/T