How severe is CVE-2026-9749?

CVE-2026-9749 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-9749 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (19th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-9749?

CVE-2026-9749 affects Mongodb. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-9749?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-9749 have an EU (EUVD) identifier?

Yes. CVE-2026-9749 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-35865.

When was CVE-2026-9749 published?

CVE-2026-9749 was published on 2026-06-09 and last updated on 2026-06-18.

CVE-2026-9749

CVE-2026-9749 is a medium-severity vulnerability in Mongodb with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-617.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v4: 7.1
EPSS exploit prediction: 0% (19th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-35865
Weakness: CWE-617
Affected product: Mongodb
Published: 2026-06-09
Last modified: 2026-06-18

Description

This issue can occur when running an aggregation pipeline that uses the internal $exchange stage configured with key-range partitioning and order-preserving delivery. If a single key range produces enough documents to fill its exchange buffer (that is, many results are routed to the same consumer), the server reaches the code path where a full per-consumer buffer is detected but the internal "high watermark" for that key range is not updated as intended.

Frequently asked questions

What is CVE-2026-9749?: This issue can occur when running an aggregation pipeline that uses the internal $exchange stage configured with key-range partitioning and order-preserving delivery. If a single key range produces enough documents to fill its exchange buffer (that is, many results are routed to the same consumer), the server reaches the code path where a full per-consumer buffer is detected but the internal "high watermark" for that key range is not updated as intended.
How severe is CVE-2026-9749?: CVE-2026-9749 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-9749 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (19th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-9749?: CVE-2026-9749 affects Mongodb. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-9749?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-9749 have an EU (EUVD) identifier?: Yes. CVE-2026-9749 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-35865.
When was CVE-2026-9749 published?: CVE-2026-9749 was published on 2026-06-09 and last updated on 2026-06-18.

References

https://jira.mongodb.org/browse/SERVER-124031

Affected products (1)

cpe:2.3:a:mongodb:mongodb:*:*:*:*:-:*:*:*

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