← Vulnerability feed

Vulnerability record · CVE-2016-2774 · published 9 March 2016

CVE-2016-2774: ISC DHCP lacks TCP session limit, enabling denial of service

Isc · Dhcp

ISC DHCP 4.1.x before 4.1-ESV-R13 and 4.2.x/4.3.x before 4.3.4 does not restrict the number of concurrent TCP sessions. A remote attacker can open many sessions to trigger an INSIST assertion failure or a request-processing outage, taking the DHCP service down.

5.9 CVSS 3.1 Medium EPSS 74% · top 0.5% CWE-20 · Improper input validation
5.9CVSS 3.1 base score, v2 7.1
74%EPSS exploitation probability, 30 days
NoNot in CISA KEV
3Affected product versions listed by NVD
20References
17 Jun 2026Last modified by NVD

Description

ISC DHCP 4.1.x before 4.1-ESV-R13 and 4.2.x and 4.3.x before 4.3.4 does not restrict the number of concurrent TCP sessions, which allows remote attackers to cause a denial of service (INSIST assertion failure or request-processing outage) by establishing many sessions.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 18 September 2026. Confidence: high.

medium priorityCVSS 3.1 base score is 5.9 (Medium) with high availability impact but high attack complexity, and no KEV listing, though EPSS is very high.

What it is

ISC DHCP 4.1.x before 4.1-ESV-R13 and 4.2.x/4.3.x before 4.3.4 does not restrict the number of concurrent TCP sessions. A remote attacker can open many sessions to trigger an INSIST assertion failure or a request-processing outage, taking the DHCP service down.

Impact

An attacker can cause a denial of service, halting DHCP request processing and disrupting address assignment for clients relying on the affected server.

Attack surface

Reachable over the network (AV:N) with no authentication (PR:N) and no user interaction (UI:N); the attacker only needs to establish many concurrent TCP sessions to the DHCP service.

Exploitation

Not listed in CISA KEV and no public exploit tags appear in the references, but EPSS is high (0.73622, 99.4th percentile), indicating elevated predicted exploitation likelihood.

What to do

  • Upgrade ISC DHCP to 4.1-ESV-R13 or 4.3.4 (or later) as applicable to your branch.
  • Apply vendor updates for Debian, Ubuntu, Red Hat, Fedora, openSUSE and Oracle distributions carrying the affected DHCP packages.
  • Restrict network access to the DHCP service to trusted clients and management networks where feasible.
  • Monitor and rate-limit concurrent TCP sessions to the DHCP service to blunt session-flood attempts.

Detection

  • Alert on a sudden spike in concurrent TCP sessions to the DHCP service.
  • Monitor DHCP service logs for INSIST assertion failures or request-processing outages.
  • Track DHCP server availability and client address-assignment failures for signs of an outage.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.

Affected products

3 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://lists.fedoraproject.org/pipermail/package-announce/2016-May/183458.html Third Party Advisory
http://lists.fedoraproject.org/pipermail/package-announce/2016-May/183640.html Third Party Advisory
http://lists.opensuse.org/opensuse-updates/2016-07/msg00066.html Mailing ListThird Party Advisory
http://rhn.redhat.com/errata/RHSA-2016-2590.html Third Party Advisory
http://www.oracle.com/technetwork/topics/security/bulletinjul2016-3090568.html Third Party Advisory
http://www.securityfocus.com/bid/84208 Third Party AdvisoryVDB Entry
http://www.securitytracker.com/id/1035196 Third Party AdvisoryVDB Entry
https://kb.isc.org/article/AA-01354 Vendor Advisory
https://lists.debian.org/debian-lts-announce/2019/11/msg00023.html Third Party Advisory
https://usn.ubuntu.com/3586-1/ Third Party Advisory
http://lists.fedoraproject.org/pipermail/package-announce/2016-May/183458.html Third Party Advisory
http://lists.fedoraproject.org/pipermail/package-announce/2016-May/183640.html Third Party Advisory
http://lists.opensuse.org/opensuse-updates/2016-07/msg00066.html Mailing ListThird Party Advisory
http://rhn.redhat.com/errata/RHSA-2016-2590.html Third Party Advisory
http://www.oracle.com/technetwork/topics/security/bulletinjul2016-3090568.html Third Party Advisory
http://www.securityfocus.com/bid/84208 Third Party AdvisoryVDB Entry
http://www.securitytracker.com/id/1035196 Third Party AdvisoryVDB Entry
https://kb.isc.org/article/AA-01354 Vendor Advisory
https://lists.debian.org/debian-lts-announce/2019/11/msg00023.html Third Party Advisory
https://usn.ubuntu.com/3586-1/ Third Party Advisory

Track CVE-2016-2774 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2025-32433Erlang/OTP SSH server missing authentication allows remote code executionErlang/OTP SSH servers before OTP-27.3.3, OTP-26.2.5.11 and OTP-25.3.2.20 mishandle SSH protocol messages, letting an unauthenticated attacker execut…KEVEPSS 99%analysed10.0CVE-2025-24201Apple WebKit out-of-bounds write allows sandbox escapeCVE-2025-24201 is an out-of-bounds write in Apple's WebKit that was addressed with improved checks. Maliciously crafted web content may break out of …KEVEPSS 3.8%analysed10.0CVE-2021-44228Apache Log4j2 JNDI lookup remote code executionApache Log4j2 versions 2.0-beta9 through 2.15.0 (excluding 2.12.2, 2.12.3, and 2.3.1) do not protect against attacker-controlled LDAP and other JNDI …KEVEPSS 100%analysed9.8CVE-2026-24061GNU Inetutils telnetd argument injection allows remote auth bypasstelnetd in GNU Inetutils through 2.7 fails to sanitize the USER environment variable, so a value such as "-f root" is passed as an argument to login …KEVEPSS 99%analysed9.8CVE-2025-39682Linux kernel TLS zero-length record handling flaw on rx_listThe Linux kernel TLS receive path mishandles zero-length records that arrive from the rx_list, breaking the assumption that a record type change cann…KEVEPSS 2.9%analysed9.8CVE-2025-24813Apache Tomcat Default Servlet path equivalence enables RCE and file disclosureApache Tomcat mishandles path equivalence for names containing an internal dot, letting a remote unauthenticated attacker write files through the Def…KEVEPSS 100%analysed9.8CVE-2024-9680Mozilla Firefox and Thunderbird use-after-free in Animation timelinesA use-after-free flaw in Animation timelines allows an attacker to execute code in the content process of Firefox and Thunderbird. Mozilla reports ex…KEVEPSS 23%analysed9.8CVE-2023-46604Apache ActiveMQ OpenWire deserialization remote code executionThe Java OpenWire protocol marshaller in Apache ActiveMQ deserializes untrusted data, letting an attacker manipulate serialized class types so the br…KEVEPSS 100%analysed

Source: NIST National Vulnerability Database (record CVE-2016-2774), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.