How severe is CVE-2026-1527?

CVE-2026-1527 has a CVSS 3.x base score of 4.6, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-1527 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-1527?

CVE-2026-1527 affects Nodejs Undici. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-1527?

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

Does CVE-2026-1527 have an EU (EUVD) identifier?

Yes. CVE-2026-1527 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11701.

When was CVE-2026-1527 published?

CVE-2026-1527 was published on 2026-03-12 and last updated on 2026-06-17.

CVE-2026-1527

CVE-2026-1527 is a medium-severity vulnerability in Nodejs Undici with a CVSS 3.x base score of 4.6. 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-93.

Key facts

Severity: Medium (CVSS 3.x base score 4.6)
EPSS exploit prediction: 0% (17th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-11701
Weakness: CWE-93
Affected product: Nodejs Undici
Published: 2026-03-12
Last modified: 2026-06-17

Description

ImpactWhen an application passes user-controlled input to the upgrade option of client.request(), an attacker can inject CRLF sequences (\r\n) to: * Inject arbitrary HTTP headers * Terminate the HTTP request prematurely and smuggle raw data to non-HTTP services (Redis, Memcached, Elasticsearch) The vulnerability exists because undici writes the upgrade value directly to the socket without validating for invalid header characters: // lib/dispatcher/client-h1.js:1121 if (upgrade) { header += `connection: upgrade\r\nupgrade: ${upgrade}\r\n` }

Frequently asked questions

What is CVE-2026-1527?: ImpactWhen an application passes user-controlled input to the upgrade option of client.request(), an attacker can inject CRLF sequences (\r\n) to: * Inject arbitrary HTTP headers * Terminate the HTTP request prematurely and smuggle raw data to non-HTTP services (Redis, Memcached, Elasticsearch) The vulnerability exists because undici writes the upgrade value directly to the socket without validating for invalid header characters: // lib/dispatcher/client-h1.js:1121 if (upgrade) { header += `connection: upgrade\r\nupgrade: ${upgrade}\r\n` }
How severe is CVE-2026-1527?: CVE-2026-1527 has a CVSS 3.x base score of 4.6, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-1527 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-1527?: CVE-2026-1527 affects Nodejs Undici. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-1527?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-1527 have an EU (EUVD) identifier?: Yes. CVE-2026-1527 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11701.
When was CVE-2026-1527 published?: CVE-2026-1527 was published on 2026-03-12 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:*

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