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CVE-2025-38468

Vulnérabilité non évaluée dans Linux (Linux)

CVSS 0.0 · Non évaluée
EPSS 0.2%
Linux•Linux•Versions : 6.1.147, <=6.1.*, <2.6.29, <=6.12.*, 6.6.100, <e5c480dc62a3025b8428d4818e722da30ad6804f, <3691f84269a23f7edd263e9b6edbc27b7ae332f4, 0, 512bb43eb5422ee69a1be05ea0d89dc074fac9a2, <850226aef8d28a00cf966ef26d2f8f2bff344535, <=6.15.*, 5.4.297, 2.6.29, 6.15.8, <fed3570e548a6c9f95c5f4c9e1a7afc1679fd90d, <=5.10.*, <=6.6.*, 5.15.190, <=5.4.*, 6.16, 6.12.40, 5.10.241, <=*, <=5.15.*, <7ff2d83ecf2619060f30ecf9fad4f2a700fca344, <890a5d423ef0a7bd13447ceaffad21189f557301, <0e1d5d9b5c5966e2e42e298670808590db5ed628, <5c0506cd1b1a3b145bda2612bbf7fe78d186c355

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: Return NULL when htb_lookup_leaf encounters an empty rbtree htb_lookup_leaf has a BUG_ON that can trigger with the following: tc qdisc del dev lo root tc qdisc add dev lo root handle 1: htb default 1 tc class add dev lo parent 1: classid 1:1 htb rate 64bit tc qdisc add dev lo parent 1:1 handle 2: netem tc qdisc add dev lo parent 2:1 handle 3: blackhole ping -I lo -c1 -W0.001 127.0.0.1 The root cause is the following: 1. htb_dequeue calls htb_dequeue_tree which calls the dequeue handler on the selected leaf qdisc 2. netem_dequeue calls enqueue on the child qdisc 3. blackhole_enqueue drops the packet and returns a value that is not just NET_XMIT_SUCCESS 4. Because of this, netem_dequeue calls qdisc_tree_reduce_backlog, and since qlen is now 0, it calls htb_qlen_notify -> htb_deactivate -> htb_deactiviate_prios -> htb_remove_class_from_row -> htb_safe_rb_erase 5. As this is the only class in the selected hprio rbtree, __rb_change_child in __rb_erase_augmented sets the rb_root pointer to NULL 6. Because blackhole_dequeue returns NULL, netem_dequeue returns NULL, which causes htb_dequeue_tree to call htb_lookup_leaf with the same hprio rbtree, and fail the BUG_ON The function graph for this scenario is shown here: 0) | htb_enqueue() { 0) + 13.635 us | netem_enqueue(); 0) 4.719 us | htb_activate_prios(); 0) # 2249.199 us | } 0) | htb_dequeue() { 0) 2.355 us | htb_lookup_leaf(); 0) | netem_dequeue() { 0) + 11.061 us | blackhole_enqueue(); 0) | qdisc_tree_reduce_backlog() { 0) | qdisc_lookup_rcu() { 0) 1.873 us | qdisc_match_from_root(); 0) 6.292 us | } 0) 1.894 us | htb_search(); 0) | htb_qlen_notify() { 0) 2.655 us | htb_deactivate_prios(); 0) 6.933 us | } 0) + 25.227 us | } 0) 1.983 us | blackhole_dequeue(); 0) + 86.553 us | } 0) # 2932.761 us | qdisc_warn_nonwc(); 0) | htb_lookup_leaf() { 0) | BUG_ON(); ------------------------------------------ The full original bug report can be seen here [1]. We can fix this just by returning NULL instead of the BUG_ON, as htb_dequeue_tree returns NULL when htb_lookup_leaf returns NULL. [1] https://lore.kernel.org/netdev/pF5XOOIim0IuEfhI-SOxTgRvNoDwuux7UHKnE_Y5-zVd4wmGvNk2ceHjKb8ORnzw0cGwfmVu42g9dL7XyJLf1NEzaztboTWcm0Ogxuojoeo=@willsroot.io/

Gravité et risque d'exploitation

CVE-2025-38468 obtient un score CVSS de 0.0/10, soit une gravité non évaluée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.18 %, ce qui la place devant 7.2 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions 6.1.147, <=6.1.*, <2.6.29, <=6.12.*, 6.6.100, <e5c480dc62a3025b8428d4818e722da30ad6804f, <3691f84269a23f7edd263e9b6edbc27b7ae332f4, 0, 512bb43eb5422ee69a1be05ea0d89dc074fac9a2, <850226aef8d28a00cf966ef26d2f8f2bff344535, <=6.15.*, 5.4.297, 2.6.29, 6.15.8, <fed3570e548a6c9f95c5f4c9e1a7afc1679fd90d, <=5.10.*, <=6.6.*, 5.15.190, <=5.4.*, 6.16, 6.12.40, 5.10.241, <=*, <=5.15.*, <7ff2d83ecf2619060f30ecf9fad4f2a700fca344, <890a5d423ef0a7bd13447ceaffad21189f557301, <0e1d5d9b5c5966e2e42e298670808590db5ed628, <5c0506cd1b1a3b145bda2612bbf7fe78d186c355) 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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