CVE-2026-84933

CVE-2026-84933 is a medium-severity vulnerability in Nodejs Undici 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-200.

Key facts

Description

undici's cache interceptor does not handle the Set-Cookie response header anywhere in its cache path, so it neither refuses to store nor strips that header. In shared cache mode, which is the default, an otherwise cacheable response that carries a Set-Cookie header, for example one marked with a public and max-age directive, is stored and then re-served to a later caller that matches the same cache key. As a result one caller's cookie is disclosed to a different caller, and an untrusted server can inject cookies into cached responses served to all subsequent callers. This violates the requirement that a shared cache must not store cookies. This affects undici versions from 7.0.0 up to 7.29.1 and from 8.0.0 up to 8.10.2. Users should upgrade to undici 7.29.1 or 8.10.2.

Frequently asked questions

What is CVE-2026-84933?
undici's cache interceptor does not handle the Set-Cookie response header anywhere in its cache path, so it neither refuses to store nor strips that header. In shared cache mode, which is the default, an otherwise cacheable response that carries a Set-Cookie header, for example one marked with a public and max-age directive, is stored and then re-served to a later caller that matches the same cache key. As a result one caller's cookie is disclosed to a different caller, and an untrusted server can inject cookies into cached responses served to all subsequent callers. This violates the requirement that a shared cache must not store cookies. This affects undici versions from 7.0.0 up to 7.29.1 and from 8.0.0 up to 8.10.2. Users should upgrade to undici 7.29.1 or 8.10.2.
How severe is CVE-2026-84933?
CVE-2026-84933 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity low, and availability none.
Is CVE-2026-84933 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-2026-84933?
CVE-2026-84933 affects Nodejs Undici. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-84933?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2026-84933 published?
CVE-2026-84933 was published on 2026-09-04 and last updated on 2026-09-15.

References

Affected products (1)

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