Cisco IOS and IOS XE Software TCP Denial of Service Vulnerability
A vulnerability in the TCP socket code of Cisco IOS and IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to a state condition between the socket state and the transmission control block (TCB) state. While this vulnerability potentially affects all TCP applications, the only affected application observed so far is the HTTP server. An attacker could exploit this vulnerability by sending specific HTTP requests at a sustained rate to a reachable IP address of the affected software. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition on an affected device.
- Published
- Jan 9, 2019
- Updated
- Jun 16, 2026
- EPSS
- 2.0% · 80th percentile
- CWE
- CWE-371
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Report tools
Action score
28
Monitor
Low priority for now.
- CVSS
- 27 / 40 · 6.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 1 / 30 · 2.0%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 6.8
- CNA · cisco
- 6.8
- agree
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| cisco | ios | cpe:2.3:o:cisco:ios |
| cisco | ios xe | cpe:2.3:o:cisco:ios_xe |
| cisco | catalyst 2960-plus 24lc-l | cpe:2.3:h:cisco:catalyst_2960-plus_24lc-l |
| cisco | catalyst 2960-plus 24lc-s | cpe:2.3:h:cisco:catalyst_2960-plus_24lc-s |
| cisco | catalyst 2960-plus 24pc-l | cpe:2.3:h:cisco:catalyst_2960-plus_24pc-l |
| cisco | catalyst 2960-plus 24pc-s | cpe:2.3:h:cisco:catalyst_2960-plus_24pc-s |
| cisco | catalyst 2960-plus 24tc-l | cpe:2.3:h:cisco:catalyst_2960-plus_24tc-l |
| cisco | catalyst 2960-plus 24tc-s | cpe:2.3:h:cisco:catalyst_2960-plus_24tc-s |
| cisco | catalyst 2960-plus 48pst-l | cpe:2.3:h:cisco:catalyst_2960-plus_48pst-l |
| cisco | catalyst 2960-plus 48pst-s | cpe:2.3:h:cisco:catalyst_2960-plus_48pst-s |
| cisco | catalyst 2960-plus 48tc-l | cpe:2.3:h:cisco:catalyst_2960-plus_48tc-l |
| cisco | catalyst 2960-plus 48tc-s | cpe:2.3:h:cisco:catalyst_2960-plus_48tc-s |
and 137 more
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- cisco ios15.2(2)e4
- cisco ios xeall versions
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.
Cisco Cisco IOS
- n/aaffected
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-2017-12240The DHCP relay subsystem of Cisco IOS 12.2 through 15.6 and Cisco IOS XE Software contains a vulnerability that could allow an unauthenticatKEV73This 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
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
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.
No dated events beyond publication.
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.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- high · the service can be disrupted
Impact can extend beyond the vulnerable component (scope changes).
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
CWE-371 · State IssuesCVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/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.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
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/106510
- tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190109-tcp
Vendor advisories and official records. Exploit/PoC links are deliberately left out.