CVE-2021-45486

Information disclosure via undersized IP-ID hash table

Published Dec 25, 2021 · Updated Aug 4, 2024

Information disclosure in the Linux kernel before 5.12.4 allows remote attackers to infer internal state via observed IPv4 IP-ID values. The ip_rt_init path in net/ipv4/route.c allocates only 2,048 IP-ID hash buckets, causing unrelated flows to share counters that expose global protocol state. Exploitation requires repeated network probes and IP-ID observations; disclosure is limited to protocol-state inferences and covert-channel uses.

CVSS severity3.5
Low
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Information disclosure in the Linux kernel before 5.12.4 allows remote attackers to infer internal state via observed IPv4 IP-ID values. The ip_rt_init path in net/ipv4/route.c allocates only 2,048 IP-ID hash buckets, causing unrelated flows to share counters that expose global protocol state. Exploitation requires repeated network probes and IP-ID observations; disclosure is limited to protocol-state inferences and covert-channel uses.

The record

CVE
CVE-2021-45486
Published
Dec 25, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-327
Attack vector
adjacent
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 25, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

2.7NIST NVDAV:A/AC:L/Au:S/C:P/I:N/A:N
3.5NIST NVDCVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
3.5OracleCVSS:3.0/AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-327Use of a Broken or Risky Cryptographic Algorithm

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo