# tipc: reject invalid and unexpected GRP_ACK_MSG to prevent bc_ackers underflow

CVE record · `CVE-2026-98550`

- **Identifiers:** `CVE-2026-98550`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **CNA:** Linux
- **Technologies:** [Linux kernel](https://agentprime.io/advisories/technology/linux-kernel.md)
- **Published:** 18 Oct 2026
- **Updated:** 24 Oct 2026
- **Reviewed by a person:** No

Published by the CVE Program (CNA: Linux) at 18 Oct 2026, 15:18 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

## Affected products, as the CNA wrote them

- Vendor: Linux. Product: Linux.
  - affected: `2f487712b89376fce267223bbb0db93d393d4b09 to before edc6593c442278fceff0120e8cc58bc592168c35` (git)
  - affected: `2f487712b89376fce267223bbb0db93d393d4b09 to before 9b94a90651e1fa573c6ac6a5a6b269d5874df2c0` (git)
  - affected: `2f487712b89376fce267223bbb0db93d393d4b09 to before 507a27435b2bb1f22e3a3674f6a6553eb815021b` (git)
  - affected: `2f487712b89376fce267223bbb0db93d393d4b09 to before 80a9ccfc24d3776ef6753a57315e726475fac7d7` (git)
  - affected: `2f487712b89376fce267223bbb0db93d393d4b09 to before 478fb08d0c2a53002a721d22b8d6681ec971d90f` (git)
  - affected: `2f487712b89376fce267223bbb0db93d393d4b09 to before 12cc3a1eac5a2a06b67a7b85f0f48ff241a94d1b` (git)
  - affected: `2f487712b89376fce267223bbb0db93d393d4b09 to before b0e517961f09b9f60d338d1ea4e17aacdbf206f0` (git)
  - affected: `2f487712b89376fce267223bbb0db93d393d4b09 to before 99cc2a62e07a44a22254d7beca9ef1f8ad886d0d` (git)
  - Other versions: unaffected
- Vendor: Linux. Product: Linux.
  - affected: `4.15`
  - unaffected: `before 4.15` (semver)
  - unaffected: `5.10.271 to 5.10.*, inclusive` (semver)
  - unaffected: `5.15.222 to 5.15.*, inclusive` (semver)
  - unaffected: `6.1.189 to 6.1.*, inclusive` (semver)
  - unaffected: `6.6.158 to 6.6.*, inclusive` (semver)
  - unaffected: `6.12.112 to 6.12.*, inclusive` (semver)
  - unaffected: `6.18.55 to 6.18.*, inclusive` (semver)
  - unaffected: `7.2.9 to 7.2.*, inclusive` (semver)
  - unaffected: `7.3 to *, inclusive` (original_commit_for_fix)
  - Other versions: affected

## Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

## Severity and exploitation

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`, from CNA (Linux)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0068, the 52nd percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the CVE Program, published 18 Oct 2026. New records show when each source confirmed them.

## Sources

- [CVE List: CVE-2026-98550](https://www.cve.org/CVERecord?id=CVE-2026-98550)
- [NVD: CVE-2026-98550](https://nvd.nist.gov/vuln/detail/CVE-2026-98550)

### References from the CNA

- <https://git.kernel.org/stable/c/edc6593c442278fceff0120e8cc58bc592168c35>
- <https://git.kernel.org/stable/c/9b94a90651e1fa573c6ac6a5a6b269d5874df2c0>
- <https://git.kernel.org/stable/c/507a27435b2bb1f22e3a3674f6a6553eb815021b>
- <https://git.kernel.org/stable/c/80a9ccfc24d3776ef6753a57315e726475fac7d7>
- <https://git.kernel.org/stable/c/478fb08d0c2a53002a721d22b8d6681ec971d90f>
- <https://git.kernel.org/stable/c/12cc3a1eac5a2a06b67a7b85f0f48ff241a94d1b>
- <https://git.kernel.org/stable/c/b0e517961f09b9f60d338d1ea4e17aacdbf206f0>
- <https://git.kernel.org/stable/c/99cc2a62e07a44a22254d7beca9ef1f8ad886d0d>

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.

## Check whether this affects you

This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it. Compare the affected versions above with what you run.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), `get_advisory` returns this record and `search_advisories` finds related ones. Setup: <https://agentprime.io/mcp.md>
- As JSON: <https://api.agentprime.io/v1/advisories/CVE-2026-98550>
- Everything that needs attention now: <https://agentprime.io/advisories/critical.md>

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The web page: <https://agentprime.io/advisories/CVE-2026-98550/>. Everything for agents: <https://agentprime.io/llms.txt>.