The DHCP relay subsystem of Cisco IOS 12.2 through 15.6 and Cisco IOS XE Software contains a vulnerability that could allow an unauthenticat
The DHCP relay subsystem of Cisco IOS 12.2 through 15.6 and Cisco IOS XE Software contains a vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary code and gain full control of an affected system. The attacker could also cause an affected system to reload, resulting in a denial of service (DoS) condition. The vulnerability is due to a buffer overflow condition in the DHCP relay subsystem of the affected software. An attacker could exploit this vulnerability by sending a crafted DHCP Version 4 (DHCPv4) packet to an affected system. A successful exploit could allow the attacker to execute arbitrary code and gain full control of the affected system or cause the affected system to reload, resulting in a DoS condition. Cisco Bug IDs: CSCsm45390, CSCuw77959.
- Published
- Sep 28, 2017
- Updated
- Jun 16, 2026
- EPSS
- 13.8% · 96th percentile
- CWE
- CWE-20
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Action score
73
This week
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- CVSS
- 39 / 40 · 9.8 / 10
- CISA KEV
- 30 / 30 · Listed
- EPSS
- 4 / 30 · 13.8%
CISA SSVC decision
- Exploitation
- active
- Automatable
- yes
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
Actively exploited in the wild
CISA added this to its Known Exploited Vulnerabilities catalog on Mar 3, 2022. That signals real attacks, not theory.
Remediation deadline for government agencies: Mar 24, 2022.
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| cisco | asr 907 | cpe:2.3:h:cisco:asr_907 |
| cisco | ios | cpe:2.3:o:cisco:ios |
| cisco | 1000 integrated services router | cpe:2.3:h:cisco:1000_integrated_services_router |
| cisco | 1100-4g integrated services router | cpe:2.3:h:cisco:1100-4g_integrated_services_router |
| cisco | 1100-4gltegb integrated services router | cpe:2.3:h:cisco:1100-4gltegb_integrated_services_router |
| cisco | 1100-4gltena integrated services router | cpe:2.3:h:cisco:1100-4gltena_integrated_services_router |
| cisco | 1100-4p integrated services router | cpe:2.3:h:cisco:1100-4p_integrated_services_router |
| cisco | 1100-6g integrated services router | cpe:2.3:h:cisco:1100-6g_integrated_services_router |
| cisco | 1100-8p integrated services router | cpe:2.3:h:cisco:1100-8p_integrated_services_router |
| cisco | 1100-lte integrated services router | cpe:2.3:h:cisco:1100-lte_integrated_services_router |
| cisco | 1100 integrated services router | cpe:2.3:h:cisco:1100_integrated_services_router |
| cisco | 1101-4p integrated services router | cpe:2.3:h:cisco:1101-4p_integrated_services_router |
and 188 more
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- cisco ios12.2 and later · up to 15.6 inclusive
Versions reported by the vendor
Affected version ranges reported by the assigning authority (cisco). Independent of NVD's CPE analysis and usually ahead of it.
n/a Cisco IOS and IOS XE
- Cisco IOS and IOS XEaffected
Same product
cisco: all recordsOther highest-scoring records for the same primary product.
- CVE-2018-0171A vulnerability in the Smart Install feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attackerKEV99Now
- CVE-2017-3881A vulnerability in the Cisco Cluster Management Protocol (CMP) processing code in Cisco IOS and Cisco IOS XE Software could allow an unautheKEV99Now
- CVE-2017-6736The Simple Network Management Protocol (SNMP) subsystem of Cisco IOS and IOS XE Software contains multiple vulnerabilities that could allow KEV86Now
- CVE-2016-6415The server IKEv1 implementation in Cisco IOS 12.2 through 12.4 and 15.0 through 15.6, IOS XE through 3.18S, IOS XR 4.3.x and 5.0.x through 5KEV86Now
- CVE-2017-6737A vulnerability in the SNMP implementation of could allow an authenticated, remote attacker to cause a reload of the affected system or to rKEV79This week
- CVE-2008-4128Multiple cross-site request forgery (CSRF) vulnerabilities in the HTTP Administration component in Cisco IOS 12.4 on the 871 Integrated ServKEV72This week
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
No fix version is recorded for this entry. Check the references for vendor advisories.
Exploit status
Weaponized
A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
- Published
- CISA KEV+1616 d
- TodaySep 30, 2026+3289 d
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-20 · Improper Input ValidationCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- Buffer Overflow via Environment VariablesCAPEC-10likelihood: High · High
- Server Side Include (SSI) InjectionCAPEC-101likelihood: High · High
- Cross Zone ScriptingCAPEC-104likelihood: Medium · High
- Command Line Execution through SQL InjectionCAPEC-108likelihood: Low · Very High
- Object Relational Mapping InjectionCAPEC-109likelihood: Low · High
- SQL Injection through SOAP Parameter TamperingCAPEC-110likelihood: High · Very High
- Double EncodingCAPEC-120likelihood: Low · Medium
- Subverting Environment Variable ValuesCAPEC-13likelihood: High · Very High
ATT&CK techniques
- Obfuscated Files or InformationT1027
- Masquerading: Invalid Code SignatureT1036.001
- Steal Web Session CookieT1539
- Subvert Trust Controls: Code SigningT1553.002
- Impair Defenses:Impair Command History LoggingT1562.003
- Hijack Execution Flow:Dynamic Linker HijackingT1574.006
- Hijack Execution Flow:Path Interception by PATH Environment VariableT1574.007
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.
References
- www.securityfocus.com/bid/101034
- www.securitytracker.com/id/1039445
- quickview.cloudapps.cisco.com/quickview/bug/CSCsm45390
- quickview.cloudapps.cisco.com/quickview/bug/CSCuw77959
- tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-dhcp
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2017-12240
Vendor advisories and official records. Exploit/PoC links are deliberately left out.