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CVE-2026-98550

Vulnerability in Linux kernel (CVE-2026-98550)

Summary

Vulnerability in Linux kernel (CVE-2026-98550). Risk of unauthorized operations or information disclosure.

Original description

The description as published by the source.

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

tipc: reject invalid and unexpected GRP_ACK_MSG to prevent bc_ackers underflow

Commit 48a5fe38772b ("tipc: fix bc_ackers underflow on duplicate
GRP_ACK_MSG") rejected duplicate/stale ACKs in tipc_group_proto_rcv()
by returning early when less_eq(acked, m->bc_acked).

However, that check remains incomplete in two ways:

  1. When grp->bc_ackers is zero (e.g. on a quiet group, when replicast
    ACKs were not requested, or after all expected members have already
    acknowledged), an unexpected GRP_ACK_MSG with acked > m->bc_acked
    passes less_eq() and unconditionally decrements grp->bc_ackers.
    Because bc_ackers is a u16, this wraps to 65535, causing
    tipc_group_bc_cong() to permanently report congestion and blocking
    all future group broadcasts on the socket.

  2. During an active broadcast round (grp->bc_ackers > 0), the sender
    transmits packet S and advances grp->bc_snd_nxt to S + 1. Receivers
    increment their expected counter to S + 1 upon consuming packet S,
    so the only valid ACK value for the current round is strictly
    acked == grp->bc_snd_nxt.

    However, tipc_group_update_bc_members() initializes each member's
    m->bc_acked to prev = grp->bc_snd_nxt - 1 (S - 1 before increment).
    This leaves a 2-sequence gap (S - 1 to S + 1) in sequence space.
    An incoming ACK is therefore neither rejected as duplicate nor
    prevented from decrementing grp->bc_ackers if an unexpected or stale
    v…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-98550 has been found in Linux kernel.
Risk of unauthorized operations or information disclosure.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-98550" on the vendor's site.

CVE-2026-98550 (Linux kernel)
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (unclassified) exists in Linux kernel.

📍 Affected scope

Check the vendor advisory for the affected versions of Linux kernel.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。

  2. 2
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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