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CVE-2026-98550

Vulnérabilité non évaluée dans Linux (Linux)

CVSS 0.0 · Non évaluée
Linux•Linux•Versions : <80a9ccfc24d3776ef6753a57315e726475fac7d7, <=6.1.*, <=6.12.*, 6.18.55, 0, <99cc2a62e07a44a22254d7beca9ef1f8ad886d0d, 6.12.112, 5.10.271, <9b94a90651e1fa573c6ac6a5a6b269d5874df2c0, 6.6.158, <=5.10.*, <=6.6.*, 6.1.189, <edc6593c442278fceff0120e8cc58bc592168c35, <478fb08d0c2a53002a721d22b8d6681ec971d90f, <12cc3a1eac5a2a06b67a7b85f0f48ff241a94d1b, <=6.18.*, 5.15.222, <507a27435b2bb1f22e3a3674f6a6553eb815021b, <=7.2.*, 2f487712b89376fce267223bbb0db93d393d4b09, 7.2.9, <=*, <=5.15.*, <b0e517961f09b9f60d338d1ea4e17aacdbf206f0, <4.15, 4.15, 7.3

Description

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 value (such as S) is received. A member sending acked = S followed by acked = S + 1 could decrement grp->bc_ackers twice in the same round, prematurely clearing bc_ackers or underflowing it. Fix this by: - Dropping GRP_ACK_MSG immediately if grp->bc_ackers is zero. - Requiring acked == grp->bc_snd_nxt and rejecting duplicates where m->bc_acked == acked. Because replicast broadcast rounds are strictly sequential, only grp->bc_snd_nxt can be acknowledged, and each member can acknowledge at most once per round. Note that a related pre-existing issue in tipc_group_delete_member() (where grp->bc_ackers decrementing to zero upon member departure does not restore *grp->open or trigger a socket wakeup) will be addressed in a separate patch.

Gravité et risque d'exploitation

CVE-2026-98550 obtient un score CVSS de 0.0/10, soit une gravité non évaluée.

Que faire ?

  • Vérifiez si Linux (versions <80a9ccfc24d3776ef6753a57315e726475fac7d7, <=6.1.*, <=6.12.*, 6.18.55, 0, <99cc2a62e07a44a22254d7beca9ef1f8ad886d0d, 6.12.112, 5.10.271, <9b94a90651e1fa573c6ac6a5a6b269d5874df2c0, 6.6.158, <=5.10.*, <=6.6.*, 6.1.189, <edc6593c442278fceff0120e8cc58bc592168c35, <478fb08d0c2a53002a721d22b8d6681ec971d90f, <12cc3a1eac5a2a06b67a7b85f0f48ff241a94d1b, <=6.18.*, 5.15.222, <507a27435b2bb1f22e3a3674f6a6553eb815021b, <=7.2.*, 2f487712b89376fce267223bbb0db93d393d4b09, 7.2.9, <=*, <=5.15.*, <b0e517961f09b9f60d338d1ea4e17aacdbf206f0, <4.15, 4.15, 7.3) est présent sur votre parc.
  • Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
  • À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
  • Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

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