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CVE-2026-4240· NVD / CVE Program· CNA VulDB

Open5GS CCA smf_s6b_sta_cb denial of service

Noroxi assessment

Priority: Monitor (action score 22/100)

  • 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: 0.92% (FIRST EPSS); higher than 60% 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.
  • Fixed version: n/a Open5GS 2.7.7.

Low priority for now. Upgrade to n/a Open5GS 2.7.7 or later.

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 was determined in Open5GS up to 2.7.6. The affected element is the function smf_gx_cca_cb/smf_gy_cca_cb/smf_s6b_aaa_cb/smf_s6b_sta_cb of the component CCA Handler. This manipulation causes denial of service. The attack can be initiated remotely. The exploit has been publicly disclosed and may be utilized. Upgrading to version 2.7.7 is sufficient to fix this issue. Patch name: 80eb484a6ab32968e755e628b70d1a9c64f012ec. Upgrading the affected component is recommended.

MediumCVSS 5.5 · v4.0—No exploit Fix available
Published
Mar 16, 2026
Updated
Jun 17, 2026
EPSS
0.9% · 60th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.9%

CISA SSVC decision

Exploitation
proof of concept
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · VulDB
6.9
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P

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
  • A fix has been released

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

Follow CVE-2026-4240

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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.

VendorProduct
open5gsopen5gs

Affected versions

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

  • open5gs open5gsbefore 2.7.7

Versions reported by the vendor

Affected version ranges reported by the assigning authority (VulDB). Independent of NVD's CPE analysis and usually ahead of it.

  • n/a Open5GS

    • 2.7.7not affected
    • 2.7.0, 2.7.1, 2.7.2, 2.7.3, 2.7.4, 2.7.5, 2.7.6affected

Same product

open5gs: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-28122A request-validation issue was discovered in Open5GS 2.1.3 through 2.2.x before 2.2.1.
    40Plan
  • CVE-2024-40130open5gs v2.6.4 is vulnerable to Buffer Overflow.
    39Monitor
  • CVE-2024-40129Open5GS v2.6.4 is vulnerable to Buffer Overflow.
    39Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-2523Feb 15, 2026 · Open5GS SMF gn-handler.c smf_gn_handle_create_pdp_context_request assertion
    22Monitor
  • ← EarlierCVE-2026-2524Feb 15, 2026 · Open5GS MME mme_s11_handle_create_session_response denial of service
    22Monitor
  • Later →CVE-2026-4988Mar 27, 2026 · Open5GS CCA Message smf_s6b denial of service
    11Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
n/a Open5GS2.7.7 · descriptionVendor (CNA)

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.

EPSS, last 120 days

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.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2024-51179489 days apartAn issue in Open 5GS v.2.7.1 allows a remote attacker to cause a denial of service via the Network Function Virtualizations (NFVs) such as t
    30Monitor
  • CVE-2025-8800218 days apartOpen5GS AMF esm-handler.c esm_handle_pdn_connectivity_request denial of service
    27Monitor
  • CVE-2025-8803218 days apartOpen5GS AMF gmm-sm.c gmm_state_exception denial of service
    27Monitor
  • CVE-2025-1925377 days apartOpen5GS AMF nsmf-handler.c amf_nsmf_pdusession_handle_update_sm_context denial of service
    27Monitor
  • CVE-2026-251729 days apartOpen5GS SMF types.c ogs_gtp2_parse_tft denial of service
    22Monitor
  • CVE-2026-252429 days apartOpen5GS MME mme_s11_handle_create_session_response denial of service
    22Monitor

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
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-404 · Improper Resource Shutdown or Release

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (5 more)

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

All records