How severe is CVE-2026-45078?

CVE-2026-45078 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-45078 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (3rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-45078?

CVE-2026-45078 affects Element Synapse. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-45078?

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

Does CVE-2026-45078 have an EU (EUVD) identifier?

Yes. CVE-2026-45078 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-32935.

When was CVE-2026-45078 published?

CVE-2026-45078 was published on 2026-05-28 and last updated on 2026-06-17.

CVE-2026-45078

CVE-2026-45078 is a medium-severity vulnerability in Element Synapse with a CVSS 3.x base score of 5.5. 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-770.

Key facts

Severity: Medium (CVSS 3.x base score 5.5)
CVSS v4: 6.8
EPSS exploit prediction: 0% (3rd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-32935
Weakness: CWE-770
Affected product: Element Synapse
Published: 2026-05-28
Last modified: 2026-06-17

Description

Synapse is an open source Matrix homeserver implementation. Prior to 1.152.1, local authenticated users can cause Synapse to starve other requests of CPU and lead to other requests failing, causing other users to be denied service. This vulnerability is fixed in 1.152.1.

Frequently asked questions

What is CVE-2026-45078?: Synapse is an open source Matrix homeserver implementation. Prior to 1.152.1, local authenticated users can cause Synapse to starve other requests of CPU and lead to other requests failing, causing other users to be denied service. This vulnerability is fixed in 1.152.1.
How severe is CVE-2026-45078?: CVE-2026-45078 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-45078 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (3rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-45078?: CVE-2026-45078 affects Element Synapse. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-45078?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-45078 have an EU (EUVD) identifier?: Yes. CVE-2026-45078 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-32935.
When was CVE-2026-45078 published?: CVE-2026-45078 was published on 2026-05-28 and last updated on 2026-06-17.

References

https://github.com/element-hq/synapse/security/advisories/GHSA-8q93-326v-3m7g

Affected products (1)

cpe:2.3:a:element:synapse:*:*:*:*:*:*:*:*

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