net/sched: Return NULL when htb_lookup_leaf encounters an empty rbtree
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)
CVE-2025-38468
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2025-38468
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "512bb43eb5422ee69a1be05ea0d89dc074fac9a2",
"lessThan": "fed3570e548a6c9f95c5f4c9e1a7afc1679fd90d",
"versionType": "git"
},
{
"status": "affected",
"version": "512bb43eb5422ee69a1be05ea0d89dc074fac9a2",
"lessThan": "5c0506cd1b1a3b145bda2612bbf7fe78d186c355",
"versionType": "git"
},
{
"status": "affected",
"version": "512bb43eb5422ee69a1be05ea0d89dc074fac9a2",
"lessThan": "850226aef8d28a00cf966ef26d2f8f2bff344535",
"versionType": "git"
},
{
"status": "affected",
"version": "512bb43eb5422ee69a1be05ea0d89dc074fac9a2",
"lessThan": "890a5d423ef0a7bd13447ceaffad21189f557301",
"versionType": "git"
},
{
"status": "affected",
"version": "512bb43eb5422ee69a1be05ea0d89dc074fac9a2",
"lessThan": "7ff2d83ecf2619060f30ecf9fad4f2a700fca344",
"versionType": "git"
},
{
"status": "affected",
"version": "512bb43eb5422ee69a1be05ea0d89dc074fac9a2",
"lessThan": "e5c480dc62a3025b8428d4818e722da30ad6804f",
"versionType": "git"
},
{
"status": "affected",
"version": "512bb43eb5422ee69a1be05ea0d89dc074fac9a2",
"lessThan": "3691f84269a23f7edd263e9b6edbc27b7ae332f4",
"versionType": "git"
},
{
"status": "affected",
"version": "512bb43eb5422ee69a1be05ea0d89dc074fac9a2",
"lessThan": "0e1d5d9b5c5966e2e42e298670808590db5ed628",
"versionType": "git"
}
],
"programFiles": [
"net/sched/sch_htb.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.29"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "2.6.29",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.4.297",
"versionType": "semver",
"lessThanOrEqual": "5.4.*"
},
{
"status": "unaffected",
"version": "5.10.241",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.190",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.147",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.100",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.40",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.15.8",
"versionType": "semver",
"lessThanOrEqual": "6.15.*"
},
{
"status": "unaffected",
"version": "6.16",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/sched/sch_htb.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2025-38468
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #27039 · Revision 1
- Added to Heist Feed
- Publisher date