CVE Catalog

CVE-2026-90110

CriticalCVSS 9.4
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.22%

12th percentile - higher than 12% of all known CVEs

Summary

A vulnerability exists in the Linux kernel's inetpeer rate limiting system, which stores peer entries in a Red-Black tree keyed deterministically on the remote IP address. An off-path adversary can predict the tree topology and force eviction of targeted nodes, resetting their rate-limiting token buckets, which allows bypassing IP-keyed ICMP rate limits and inferring open UDP ports. The fix randomizes the RB-tree node comparison using SipHash with a secret key.

Risk Assessment

An off-path attacker can bypass ICMP rate limits and infer open UDP ports, facilitating further attacks (similar to SAD DNS style attacks). This may lead to information disclosure about services running in the organization.

Recommendation

Update the Linux kernel to a version containing the fix that randomizes inetpeer RB-tree node comparison using SipHash. A system reboot is recommended after the update to apply the change.

Other vulnerabilities in Linux kernel

See all
Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS