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UK Cyber Defence
VulnerabilityAnalyzed

CVE-2026-109829

An attacker who controls the target of a redirect from a trusted URL can have their response cached under that trusted URL and served to later callers, allowing persistent cache poisoning, and the same key confusion lets a private, non-stored redirect…

CRITICAL 9.1EPSS 0.15%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.15%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

Description

undici is an HTTP client library for Node.js. In versions 7.0.0 through 7.30.0 and 8.0.0 through 8.12.1, when an originless Agent composes the redirect and cache interceptors in that order with a shared cache store, the cache builds its key from the original request URL before the redirect handler changes the origin, so a response produced after a cross-origin redirect is stored under the original key. An attacker who controls the target of a redirect from a trusted URL can have their response cached under that trusted URL and served to later callers, allowing persistent cache poisoning, and the same key confusion lets a private, non-stored redirect response to a user-specific resource be stored under the original URL and served to a later unauthenticated caller, disclosing private data. Applications are affected only when an originless Agent, a shared cache store, and the redirect-then-cache composition are all used. The issue is fixed in undici 7.30.1 and 8.12.2, which verify the producing origin still matches the cache key and preserve each redirect hop's cache-control policy before storing, and users should upgrade to one of those versions or later. As a workaround, compose the cache interceptor before the redirect interceptor, use per-origin dispatchers and cache stores, or disable shared caching on redirect-capable requests.

CVSS 3.1
9.1 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS
0.15% probability · 4th percentile
Public exploits
None in Exploit-DB
CISA KEV
Not listed
Weakness
CWE-346, CWE-524
Affected
nodejs/undici
Source
ce714d77-add3-4f53-aff5-83d477b104bb
EPSS trend
0%3%5%16 October 2026: 0.15%26 October 2026: 0.15%16 October 202626 October 2026

EPSS moved from 0.1% on 16 October 2026 to 0.1% on 26 October 2026.

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.