Security Resilience

CVE-2018-0156

Cisco Ios 15.2\(2\)e4 … 15.2\(2a\)ja

CISA KEVActive ExploitationEUVD Exploited
Published
28 March 2018
Modified
12 January 2026
KEV Added
03 March 2022
Patch / advisory
CVSS Score v3.1 7.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.094 95th percentile
Risk Priority 84 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2018-0156 is a high-severity Improper Input Validation (CWE-20) vulnerability in Cisco Ios. Its CVSS base score is 7.5 (High).

Operationally, ranked in the top 5% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

A vulnerability in the Smart Install feature of Cisco IOS Software and Cisco IOS XE Software stems from improper validation of packet data and can be triggered by sending a crafted packet to TCP port 4786. The flaw is tracked as Cisco Bug ID CSCvd40673 and is assigned CWE-399 and CWE-20. Only devices configured as Smart Install clients are affected; devices operating as Smart Install directors are not vulnerable. The issue received a CVSS 3.1 base score of 7.5 reflecting high availability impact with network attack vector and no required credentials.

An unauthenticated remote attacker can exploit the weakness to force an affected client switch to reload, producing a denial-of-service condition. No user interaction or local access is required, and the attack can be launched over the network against any reachable Smart Install client.

Public advisories and patches addressing the vulnerability are documented at the Cisco Security Advisory page, the ICS-CERT alerts ICSA-18-107-04 and ICSA-18-107-05, and the associated SecurityFocus and SecurityTracker entries.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

A vulnerability in the Smart Install feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to trigger a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability…

more

is due to improper validation of packet data. An attacker could exploit this vulnerability by sending a crafted packet to an affected device on TCP port 4786. Only Smart Install client switches are affected. Cisco devices that are configured as a Smart Install director are not affected by this vulnerability. Cisco Bug IDs: CSCvd40673.

CWE(s)
KEV Date Added
03 March 2022

Related Threats

CVEs Like This One

CVE-2017-3881Same product: Cisco Catalyst 2960-Plus 24Lc-Lboth on KEV
CVE-2018-0159Same product: Cisco Iosboth on KEV
CVE-2018-0161Same product: Cisco Iosboth on KEV
CVE-2017-12238Same product: Cisco Iosboth on KEV
CVE-2017-12319Same product: Cisco Iosboth on KEV
CVE-2017-12235Same product: Cisco Iosboth on KEV
CVE-2017-12234Same product: Cisco Iosboth on KEV
CVE-2017-12233Same product: Cisco Iosboth on KEV
CVE-2017-12237Same product: Cisco Iosboth on KEV
CVE-2017-12232Same product: Cisco Iosboth on KEV

Affected Assets

cisco
ios
15.2\(2\)e4, 15.2\(2a\)ja
cisco
ios xe
15.2\(2\)e4, 15.2\(2a\)ja

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-20

Security testing and developer training directly verify and enforce proper input validation, reducing exploitability of injection and malformed-data weaknesses.

addresses: CWE-20

Security testing and evaluation at multiple SDLC stages directly detects missing or flawed input validation, with the required remediation process ensuring fixes are applied.

addresses: CWE-20

Directly implements checks on information inputs to reject invalid data before processing.

addresses: CWE-20

Spam protection mechanisms perform filtering and detection on inbound/outbound messages, directly compensating for missing or weak input validation of unsolicited content.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

blocks

A.8.25 mandates security requirements, secure coding guidelines, checkpoints, testing (incl. code scans) and developer training in the SDLC, which reaches a slice of input validation defects but leaves the majority (incomplete enforcement, second-order inputs, parser differentials, post-validation canonicalization) unaddressed as in the SA-3 and A.8.28 anchors.

blocks

Mandating input controls that include integrity checks and input validation ensures that untrusted data is examined before use, blocking the root cause of many injection and malformed-data weaknesses.

blocks

Security-by-design principles explicitly call for data validation and sanitization at every layer, reducing the chance that malformed or malicious input will be processed without scrutiny.

prevents

Requiring language-specific secure coding standards, peer review, SAST and documented mitigation of common programming errors forces validation of all inputs before they are trusted.

finds

Testing against a defined set of requirements and using code review plus vulnerability scanning forces validation of inputs and handling of unanticipated conditions, reducing the chance that malformed data will be accepted.

Hardening callouts derived

DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.

  • No fine-grained STIG row for CWE-20, a class-level weakness, and none of its children carries one either.

References