Description
In the Linux kernel, the following vulnerability has been resolved:
inetpeer: randomize RB-tree node comparison using SipHash
The inetpeer rate limiting system stores peer entries in a Red-Black tree
keyed deterministically on the remote IP address. Because tree lookups walk
the RB-tree using standard lexicographical comparisons (inetpeer_addr_cmp),
an off-path adversary can predict the exact topology of the tree and the
sequence of nodes traversed during lookups (the gc_stack candidate list).
By combining deterministic tree traversal with aggressive garbage collection
(triggered when tree size exceeds inet_peer_threshold), an attacker can
selectively force the eviction of targeted inet_peer nodes. When an evicted
node is subsequently re-created upon receiving a new packet, its rate-limiting
token bucket (rate_tokens, rate_last) is reset to full capacity. This creates
a side-channel primitive allowing off-path attackers to bypass IP-keyed ICMP
rate limits and infer open UDP ports (similar to SAD DNS style attacks).
Mitigate this by randomizing the RB-tree node comparison logic using SipHash
with a secret key (inetpeer_hash_key) initialized via net_get_random_once().
Nodes are ordered in the tree by SipHash(addr, key) rather than raw IP
addresses. Because the secret key is unknown to external entities, the tree
layout and lookup traversal paths are unpredictable to off-path adversaries,
breaking the deterministic eviction gadget.
Cache the computed 64-bit SipHash (hash) in struct inet_peer and compute the
target hash (dhash) once at the beginning of inet_getpeer() to avoid recomputing
SipHash at every step of the RB-tree walk.
inetpeer: randomize RB-tree node comparison using SipHash
The inetpeer rate limiting system stores peer entries in a Red-Black tree
keyed deterministically on the remote IP address. Because tree lookups walk
the RB-tree using standard lexicographical comparisons (inetpeer_addr_cmp),
an off-path adversary can predict the exact topology of the tree and the
sequence of nodes traversed during lookups (the gc_stack candidate list).
By combining deterministic tree traversal with aggressive garbage collection
(triggered when tree size exceeds inet_peer_threshold), an attacker can
selectively force the eviction of targeted inet_peer nodes. When an evicted
node is subsequently re-created upon receiving a new packet, its rate-limiting
token bucket (rate_tokens, rate_last) is reset to full capacity. This creates
a side-channel primitive allowing off-path attackers to bypass IP-keyed ICMP
rate limits and infer open UDP ports (similar to SAD DNS style attacks).
Mitigate this by randomizing the RB-tree node comparison logic using SipHash
with a secret key (inetpeer_hash_key) initialized via net_get_random_once().
Nodes are ordered in the tree by SipHash(addr, key) rather than raw IP
addresses. Because the secret key is unknown to external entities, the tree
layout and lookup traversal paths are unpredictable to off-path adversaries,
breaking the deterministic eviction gadget.
Cache the computed 64-bit SipHash (hash) in struct inet_peer and compute the
target hash (dhash) once at the beginning of inet_getpeer() to avoid recomputing
SipHash at every step of the RB-tree walk.
Published:
2026-09-17
Score:
n/a
EPSS:
n/a
KEV:
No
Impact:
n/a
Action:
n/a
Analysis
No analysis available yet.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
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| Linux | Linux | affected |
|
No data.
No data.
No data available yet.
Remediation
No remediation available yet.
Tracking
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Advisories
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References
History
Thu, 17 Sep 2026 16:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: inetpeer: randomize RB-tree node comparison using SipHash The inetpeer rate limiting system stores peer entries in a Red-Black tree keyed deterministically on the remote IP address. Because tree lookups walk the RB-tree using standard lexicographical comparisons (inetpeer_addr_cmp), an off-path adversary can predict the exact topology of the tree and the sequence of nodes traversed during lookups (the gc_stack candidate list). By combining deterministic tree traversal with aggressive garbage collection (triggered when tree size exceeds inet_peer_threshold), an attacker can selectively force the eviction of targeted inet_peer nodes. When an evicted node is subsequently re-created upon receiving a new packet, its rate-limiting token bucket (rate_tokens, rate_last) is reset to full capacity. This creates a side-channel primitive allowing off-path attackers to bypass IP-keyed ICMP rate limits and infer open UDP ports (similar to SAD DNS style attacks). Mitigate this by randomizing the RB-tree node comparison logic using SipHash with a secret key (inetpeer_hash_key) initialized via net_get_random_once(). Nodes are ordered in the tree by SipHash(addr, key) rather than raw IP addresses. Because the secret key is unknown to external entities, the tree layout and lookup traversal paths are unpredictable to off-path adversaries, breaking the deterministic eviction gadget. Cache the computed 64-bit SipHash (hash) in struct inet_peer and compute the target hash (dhash) once at the beginning of inet_getpeer() to avoid recomputing SipHash at every step of the RB-tree walk. | |
| Title | inetpeer: randomize RB-tree node comparison using SipHash | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-17T16:06:18.113Z
Reserved: 2026-09-11T19:38:34.787Z
Link: CVE-2026-90110
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-17T17:17:02.990
Modified: 2026-09-17T17:17:02.990
Link: CVE-2026-90110
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.