NVD / CVE Program· CNA cisco

CVE-2023-20027: Cisco IOS XE Software Virtual Fragmentation Reassembly Denial of Service Vulnerability

Noroxi assessment

Priority: Monitor (action score 34/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.98% (FIRST EPSS); higher than 62.5% of all records.
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.
According to CISA the attack is automatable: targets can be found by mass scanning.
According to the record, no fixed version is available yet.
Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

A vulnerability in the implementation of the IPv4 Virtual Fragmentation Reassembly (VFR) feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper reassembly of large packets that occurs when VFR is enabled on either a tunnel interface or on a physical interface that is configured with a maximum transmission unit (MTU) greater than 4,615 bytes. An attacker could exploit this vulnerability by sending fragmented packets through a VFR-enabled interface on an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

HighCVSS 8.6 · v3.1—No exploit No fix recorded

BDU:2023-01966

Published: Mar 23, 2023
Updated: Jun 17, 2026
EPSS: 0.9% · 62th percentile
CWE: CWE-416

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 34 / 40 · 8.6 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.9%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 8.6
CNA · cisco: 8.6; agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
cisco	ios xe	cpe:2.3:o:cisco:ios_xe
cisco	catalyst 8000v edge	cpe:2.3:a:cisco:catalyst_8000v_edge
cisco	cloud services router 1000v	cpe:2.3:a:cisco:cloud_services_router_1000v
cisco	1000 integrated services router	cpe:2.3:h:cisco:1000_integrated_services_router
cisco	1100-4g\/6g integrated services router	cpe:2.3:h:cisco:1100-4g\/6g_integrated_services_router
cisco	1100-4g integrated services router	cpe:2.3:h:cisco:1100-4g_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 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
cisco	1101 integrated services router	cpe:2.3:h:cisco:1101_integrated_services_router

and 23 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

cisco ios xe16.10.1
cisco ios xe16.10.1a
cisco ios xe16.10.1b
cisco ios xe16.10.1e
cisco ios xe16.10.1s
cisco ios xe16.10.2
cisco ios xe16.10.3
cisco ios xe16.11.1
cisco ios xe16.11.1a
cisco ios xe16.11.1c
cisco ios xe16.11.1s
cisco ios xe16.11.2
cisco ios xe16.12.1
cisco ios xe16.12.1a
cisco ios xe16.12.1c
cisco ios xe16.12.1s
cisco ios xe16.12.2
cisco ios xe16.12.2s
cisco ios xe16.12.2t
cisco ios xe16.12.3

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 XE Software
- n/aaffected

Same product

cisco: all records

Other highest-scoring records for the same primary product.

CVE-2023-20198Cisco is providing an update for the ongoing investigation into observed exploitation of the web UI feature in Cisco IOS XE Software.KEV
100Now
CVE-2023-20273A vulnerability in the web UI feature of Cisco IOS XE Software could allow an authenticated, remote attacker to inject commands with the…KEV
86Now
CVE-2018-0151A vulnerability in the quality of service (QoS) subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated…KEV
73This week

Published before and after this one in the same product

← EarlierCVE-2022-20915Oct 10, 2022 · Cisco IOS XE Software IPv6 VPN over MPLS Denial of Service Vulnerability
29Monitor
← EarlierCVE-2022-20944Oct 10, 2022 · Cisco IOS XE Software for Catalyst 9200 Series Switches Arbitrary Code Execution Vulnerability
27Monitor
Later →CVE-2023-20029Mar 23, 2023 · Cisco IOS XE Software Privilege Escalation Vulnerability
31Monitor

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.

No history yet (it accumulates with the daily EPSS job).

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 researchers

Finders, 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).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

TR-23-0171 · Mar 24, 2023(Cisco Güvenlik Güncellemesi)

All national notices →

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: none
Integrity: none
Availability: high · the service can be disrupted

Impact can extend beyond the vulnerable component (scope changes).

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Changed
Confidentiality impact: None
Integrity impact: None
Availability impact: High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

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

nvd-primary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&dev->lock);

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.

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ipv4-vfr-dos-CXxtFacb

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records