CVE-2015-2923

IPv6 communication loss via unchecked hop limit

Published Feb 20, 2020 · Updated Aug 6, 2024

Improper input validation in FreeBSD through 10.1 allows remote attackers to disrupt off-link IPv6 communication via crafted router advertisements. The IPv6 Neighbor Discovery implementation accepts an advertised Current Hop Limit without rejecting an unsafe small value and replaces the interface setting with it. The attacker must be on the local network, and the interface must be manually configured to accept router advertisements; affected packets can then be dropped before reaching IPv6 nodes on other networks.

CVSS severity6.5
Medium
EPSS probability1.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in FreeBSD through 10.1 allows remote attackers to disrupt off-link IPv6 communication via crafted router advertisements. The IPv6 Neighbor Discovery implementation accepts an advertised Current Hop Limit without rejecting an unsafe small value and replaces the interface setting with it. The attacker must be on the local network, and the interface must be manually configured to accept router advertisements; affected packets can then be dropped before reaching IPv6 nodes on other networks.

The record

CVE
CVE-2015-2923
Published
Feb 20, 2020
Updated
Aug 6, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-20, T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 20, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 6, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.3NIST NVDAV:A/AC:L/Au:N/C:N/I:N/A:P

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1499.004Application or System Exploitation

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

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Your stack

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