How severe is CVE-2026-35515?

CVE-2026-35515 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity none, and availability low.

Is CVE-2026-35515 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-35515?

CVE-2026-35515 affects Nestjs Nest. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-35515?

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

Does CVE-2026-35515 have an EU (EUVD) identifier?

Yes. CVE-2026-35515 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19680.

When was CVE-2026-35515 published?

CVE-2026-35515 was published on 2026-04-07 and last updated on 2026-06-17.

CVE-2026-35515

CVE-2026-35515 is a medium-severity vulnerability in Nestjs Nest with a CVSS 3.x base score of 6.1. 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-74.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
CVSS v4: 6.3
EPSS exploit prediction: 0% (21st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-19680
Weakness: CWE-74
Affected product: Nestjs Nest
Published: 2026-04-07
Last modified: 2026-06-17

Description

Nest is a framework for building scalable Node.js server-side applications. Prior to 11.1.18, SseStream._transform() interpolates message.type and message.id directly into Server-Sent Events text protocol output without sanitizing newline characters (\r, \n). Since the SSE protocol treats both \r and \n as field delimiters and \n\n as event boundaries, an attacker who can influence these fields through upstream data sources can inject arbitrary SSE events, spoof event types, and corrupt reconnection state. This vulnerability is fixed in 11.1.18.

Frequently asked questions

What is CVE-2026-35515?: Nest is a framework for building scalable Node.js server-side applications. Prior to 11.1.18, SseStream._transform() interpolates message.type and message.id directly into Server-Sent Events text protocol output without sanitizing newline characters (\r, \n). Since the SSE protocol treats both \r and \n as field delimiters and \n\n as event boundaries, an attacker who can influence these fields through upstream data sources can inject arbitrary SSE events, spoof event types, and corrupt reconnection state. This vulnerability is fixed in 11.1.18.
How severe is CVE-2026-35515?: CVE-2026-35515 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity none, and availability low.
Is CVE-2026-35515 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-35515?: CVE-2026-35515 affects Nestjs Nest. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-35515?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-35515 have an EU (EUVD) identifier?: Yes. CVE-2026-35515 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19680.
When was CVE-2026-35515 published?: CVE-2026-35515 was published on 2026-04-07 and last updated on 2026-06-17.

References

https://github.com/nestjs/nest/security/advisories/GHSA-36xv-jgw5-4q75

Affected products (1)

cpe:2.3:a:nestjs:nest:*:*:*:*:*:node.js:*:*

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