Bug 2516908 (CVE-2026-74282)

Summary: CVE-2026-74282 kernel: tipc: prevent snt_unacked underflow on CONN_ACK
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Transparent Inter-Process Communication (TIPC) component. A remote or local attacker could send an oversized connection acknowledgment (ACK) message, leading to an integer underflow. This underflow can cause the connection to become permanently congested, effectively starving it of further transmissions and resulting in a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-08-15 06:39:46 UTC 
In the Linux kernel, the following vulnerability has been resolved:

tipc: prevent snt_unacked underflow on CONN_ACK

tipc_sk_conn_proto_rcv() subtracts the peer-supplied connection ack count
from the unsigned 16-bit send counter snt_unacked without checking that it
does not exceed the number of messages actually outstanding:

	tsk->snt_unacked -= msg_conn_ack(hdr);

msg_conn_ack() is read straight from a received CONN_MANAGER/CONN_ACK
message. If the ack count is larger than snt_unacked, the subtraction
wraps to a near-maximum value, leaving tsk_conn_cong() permanently true
and starving the connection of further transmits.

Validate the ACK count at the start of the CONN_ACK block and drop the
message if it acknowledges more messages than are outstanding. A peer (or,
for a local connection, the connected peer socket) can otherwise wedge a
TIPC connection's send side by sending an oversized connection ack.
Comment 1 Keith Grant 2026-08-20 14:07:50 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081546-CVE-2026-74282-5b9f@gregkh/T