CVE-2021-40797

Exp

An issue was discovered in the routes middleware in OpenStack Neutron before 16.4.1, 17.x before 17.2.1, and 18.x before 18.1.1. By making API requests involving nonexistent controllers, an authenticated user may cause the API worker to consume increasing amounts of memory, resulting in API performance degradation or denial of service.

Published: 2021-09-08 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]

Conclusion & alert: CVE-2021-40797 is rated High Exploit Risk (68/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.70%). Core evidence: 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +1.01% over the last day, indicating growing attacker interest. Mandatory action: Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-40797

EDB-ID Source Kind Published Link
nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-40797

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.69% 1.70% +1.01%
2 2026-05-15 0.93% 0.69% -0.24%
3 2026-05-12 0.93%

Full EPSS history (18 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-40797

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
2.8 3.6 [email protected]
4.0 2.0 MEDIUM
AV:N/AC:L/Au:S/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
8.0 2.9 [email protected]

Weakness enumeration for CVE-2021-40797

GitHub Security Advisory for CVE-2021-40797

GHSA-cpx3-696p-3cw9 · Severity: high · Ecosystem: pip — OpenStack Neutron Denial of Service vulnerability

OS Trackers for CVE-2021-40797

vendor priority summary link
debian unimportant CVE-2021-40797 unimportant priority: Debian including 1 source packages (neutron), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-40797
redhat medium https://access.redhat.com/security/cve/CVE-2021-40797
suse medium CVE-2021-40797 severity moderate: SUSE including 12 source package names (openstack-neutron-11.0.9~dev69-3.43.1, openstack-neutron-dhcp-agent-11.0.9~dev69-3.43.1, …), 36 product×package rows across 3 product lines (HPE Helion OpenStack 8, SUSE OpenStack Cloud 8, SUSE OpenStack Cloud Crowbar 8): Fixed 36. https://www.suse.com/security/cve/CVE-2021-40797/
ubuntu medium CVE-2021-40797 medium priority: Ubuntu including 1 source packages (neutron), 15 status rows across 15 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 9, released 3, DNE 1, ignored 1, needs-triage 1. https://ubuntu.com/security/CVE-2021-40797

Affected software / configurations for CVE-2021-40797

Vendor Product Version Raw CPE
openstack neutron < 16.4.1 cpe:2.3:a:openstack:neutron:*:*:*:*:*:*:*:*
openstack neutron >= 17.0.0, < 17.2.1 cpe:2.3:a:openstack:neutron:*:*:*:*:*:*:*:*
openstack neutron >= 18.0.0, < 18.1.1 cpe:2.3:a:openstack:neutron:*:*:*:*:*:*:*:*

References for CVE-2021-40797

URL Tags
http://www.openwall.com/lists/oss-security/2021/09/09/2 Mailing List Patch Third Party Advisory
https://launchpad.net/bugs/1942179 Exploit Issue Tracking Third Party Advisory
https://security.openstack.org/ossa/OSSA-2021-006.html Patch Vendor Advisory
cvelogic Threat Intelligence