{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-38468","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2025-04-16T04:51:24.020Z","datePublished":"2025-07-28T11:12:20.188Z","dateUpdated":"2026-05-12T12:05:04.146Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-05-11T21:28:35.690Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: Return NULL when htb_lookup_leaf encounters an empty rbtree\n\nhtb_lookup_leaf has a BUG_ON that can trigger with the following:\n\ntc qdisc del dev lo root\ntc qdisc add dev lo root handle 1: htb default 1\ntc class add dev lo parent 1: classid 1:1 htb rate 64bit\ntc qdisc add dev lo parent 1:1 handle 2: netem\ntc qdisc add dev lo parent 2:1 handle 3: blackhole\nping -I lo -c1 -W0.001 127.0.0.1\n\nThe root cause is the following:\n\n1. htb_dequeue calls htb_dequeue_tree which calls the dequeue handler on\n   the selected leaf qdisc\n2. netem_dequeue calls enqueue on the child qdisc\n3. blackhole_enqueue drops the packet and returns a value that is not\n   just NET_XMIT_SUCCESS\n4. Because of this, netem_dequeue calls qdisc_tree_reduce_backlog, and\n   since qlen is now 0, it calls htb_qlen_notify -> htb_deactivate ->\n   htb_deactiviate_prios -> htb_remove_class_from_row -> htb_safe_rb_erase\n5. As this is the only class in the selected hprio rbtree,\n   __rb_change_child in __rb_erase_augmented sets the rb_root pointer to\n   NULL\n6. Because blackhole_dequeue returns NULL, netem_dequeue returns NULL,\n   which causes htb_dequeue_tree to call htb_lookup_leaf with the same\n   hprio rbtree, and fail the BUG_ON\n\nThe function graph for this scenario is shown here:\n 0)               |  htb_enqueue() {\n 0) + 13.635 us   |    netem_enqueue();\n 0)   4.719 us    |    htb_activate_prios();\n 0) # 2249.199 us |  }\n 0)               |  htb_dequeue() {\n 0)   2.355 us    |    htb_lookup_leaf();\n 0)               |    netem_dequeue() {\n 0) + 11.061 us   |      blackhole_enqueue();\n 0)               |      qdisc_tree_reduce_backlog() {\n 0)               |        qdisc_lookup_rcu() {\n 0)   1.873 us    |          qdisc_match_from_root();\n 0)   6.292 us    |        }\n 0)   1.894 us    |        htb_search();\n 0)               |        htb_qlen_notify() {\n 0)   2.655 us    |          htb_deactivate_prios();\n 0)   6.933 us    |        }\n 0) + 25.227 us   |      }\n 0)   1.983 us    |      blackhole_dequeue();\n 0) + 86.553 us   |    }\n 0) # 2932.761 us |    qdisc_warn_nonwc();\n 0)               |    htb_lookup_leaf() {\n 0)               |      BUG_ON();\n ------------------------------------------\n\nThe full original bug report can be seen here [1].\n\nWe can fix this just by returning NULL instead of the BUG_ON,\nas htb_dequeue_tree returns NULL when htb_lookup_leaf returns\nNULL.\n\n[1] https://lore.kernel.org/netdev/pF5XOOIim0IuEfhI-SOxTgRvNoDwuux7UHKnE_Y5-zVd4wmGvNk2ceHjKb8ORnzw0cGwfmVu42g9dL7XyJLf1NEzaztboTWcm0Ogxuojoeo=@willsroot.io/"}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_htb.c"],"versions":[{"version":"512bb43eb5422ee69a1be05ea0d89dc074fac9a2","lessThan":"fed3570e548a6c9f95c5f4c9e1a7afc1679fd90d","status":"affected","versionType":"git"},{"version":"512bb43eb5422ee69a1be05ea0d89dc074fac9a2","lessThan":"5c0506cd1b1a3b145bda2612bbf7fe78d186c355","status":"affected","versionType":"git"},{"version":"512bb43eb5422ee69a1be05ea0d89dc074fac9a2","lessThan":"850226aef8d28a00cf966ef26d2f8f2bff344535","status":"affected","versionType":"git"},{"version":"512bb43eb5422ee69a1be05ea0d89dc074fac9a2","lessThan":"890a5d423ef0a7bd13447ceaffad21189f557301","status":"affected","versionType":"git"},{"version":"512bb43eb5422ee69a1be05ea0d89dc074fac9a2","lessThan":"7ff2d83ecf2619060f30ecf9fad4f2a700fca344","status":"affected","versionType":"git"},{"version":"512bb43eb5422ee69a1be05ea0d89dc074fac9a2","lessThan":"e5c480dc62a3025b8428d4818e722da30ad6804f","status":"affected","versionType":"git"},{"version":"512bb43eb5422ee69a1be05ea0d89dc074fac9a2","lessThan":"3691f84269a23f7edd263e9b6edbc27b7ae332f4","status":"affected","versionType":"git"},{"version":"512bb43eb5422ee69a1be05ea0d89dc074fac9a2","lessThan":"0e1d5d9b5c5966e2e42e298670808590db5ed628","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_htb.c"],"versions":[{"version":"2.6.29","status":"affected"},{"version":"0","lessThan":"2.6.29","status":"unaffected","versionType":"semver"},{"version":"5.4.297","lessThanOrEqual":"5.4.*","status":"unaffected","versionType":"semver"},{"version":"5.10.241","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.190","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.147","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.100","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.40","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.15.8","lessThanOrEqual":"6.15.*","status":"unaffected","versionType":"semver"},{"version":"6.16","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.29","versionEndExcluding":"5.4.297"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.29","versionEndExcluding":"5.10.241"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.29","versionEndExcluding":"5.15.190"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.29","versionEndExcluding":"6.1.147"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.29","versionEndExcluding":"6.6.100"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.29","versionEndExcluding":"6.12.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.29","versionEndExcluding":"6.15.8"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.29","versionEndExcluding":"6.16"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/fed3570e548a6c9f95c5f4c9e1a7afc1679fd90d"},{"url":"https://git.kernel.org/stable/c/5c0506cd1b1a3b145bda2612bbf7fe78d186c355"},{"url":"https://git.kernel.org/stable/c/850226aef8d28a00cf966ef26d2f8f2bff344535"},{"url":"https://git.kernel.org/stable/c/890a5d423ef0a7bd13447ceaffad21189f557301"},{"url":"https://git.kernel.org/stable/c/7ff2d83ecf2619060f30ecf9fad4f2a700fca344"},{"url":"https://git.kernel.org/stable/c/e5c480dc62a3025b8428d4818e722da30ad6804f"},{"url":"https://git.kernel.org/stable/c/3691f84269a23f7edd263e9b6edbc27b7ae332f4"},{"url":"https://git.kernel.org/stable/c/0e1d5d9b5c5966e2e42e298670808590db5ed628"}],"title":"net/sched: 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