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Medium

undici vulnerable to cross-user cookie disclosure via Set-Cookie caching in shared caches

  • Disclosed: 29.09.2026
  • Updated: 11.10.2026 10:22

Impact

undici's interceptors.cache() does not handle Set-Cookie in the cache path. In shared-cache mode (type: 'shared', the default), a cacheable response (for example Cache-Control: public, max-age=...) carrying a Set-Cookie header is stored, and the stored Set-Cookie is re-served to a later caller that hits the same cache key. This exposes one user's cookie to another caller and lets an untrusted upstream inject cookies into cached responses served to all subsequent callers, violating RFC 6265 section 7.2 (a shared cache must not store cookies). Applications using the shared cache interceptor against untrusted or multi-user upstreams are affected. Private caches (type: 'private') are not affected.

Patches

Upgrade to 7.29.1 or 8.10.2. In shared-cache mode, undici no longer stores or re-serves responses containing Set-Cookie, including previously cached entries and revalidation paths.

Workarounds

Use a private cache (type: 'private') for per-user responses, or avoid caching responses that set cookies. Applications acting as shared caches should strip Set-Cookie from responses before caching.

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
npm package undici >= 7.0.0, < 7.29.1, >= 8.0.0, < 8.10.2 7.29.1, 8.10.2

References

CVSS score 6.5/10
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
Weakness (CWE)
CWE-200, CWE-524
Platform
npm
Package
undici
Disclosed
29.09.2026
Updated
11.10.2026 10:22

Sources and licenses

OSV / GitHub Advisory Database - GHSA-2jfj-6hjv-fm6j - CC BY 4.0

Vulnerability history: undici

All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (46) in the archive
Total entries
46
First → latest
06.2022 09.2026
Without a fix
0
Exploited in attacks
0

Severity breakdown

  • High 13
  • Medium 21
  • Low 12

Disclosures per year

Severity:
  1. undici vulnerable to Denial of Service via unrequested WebSocket subprotocol
    High · 7.5 CVE-2026-19534 >= 6.7.0, < 6.28.1, >= 7.0.0, < 7.29.1, >= 8.0.0, < 8.10.2 6.28.1, 7.29.1, 8.10.2
  2. undici vulnerable to cross-user cookie disclosure via Set-Cookie caching in shared caches this entry
    Medium · 6.5 CVE-2026-84933 >= 7.0.0, < 7.29.1, >= 8.0.0, < 8.10.2 7.29.1, 8.10.2
  3. undici vulnerable to TLS certificate validation bypass via dropped connect options in BalancedPool
    High · 7.4 CVE-2026-84961 >= 7.24.1, < 7.29.1, >= 8.0.0, < 8.10.2 7.29.1, 8.10.2
  4. undici vulnerable to cross-origin cache poisoning via missing origin isolation in interceptors
    High · 7.4 CVE-2026-85152 >= 8.10.0, < 8.10.2 8.10.2
  5. undici vulnerable to cross-user information disclosure and parse-time crash via degenerate private cache directives
    High · 7.4 CVE-2026-13697 >= 7.0.0, < 7.29.0, >= 8.0.0, < 8.9.0 7.29.0, 8.9.0
  6. undici WebSocket client vulnerable to denial of service via fragment count bypass
    High · 7.5 CVE-2026-12151 < 6.27.0, >= 7.0.0, < 7.28.0, >= 8.0.0, < 8.5.0 6.27.0, 7.28.0, 8.5.0
  7. undici vulnerable to cross-origin request routing via SOCKS5 proxy pool reuse
    High · 7.5 CVE-2026-6734 >= 7.23.0, < 7.28.0, >= 8.0.0, < 8.2.0 7.28.0, 8.2.0
  8. undici vulnerable to TLS certificate validation bypass via dropped requestTls in SOCKS5 ProxyAgent
    High · 7.4 CVE-2026-9697 >= 7.23.0, < 7.28.0, >= 8.0.0, < 8.5.0 7.28.0, 8.5.0
  9. undici WebSocket client vulnerable to denial of service via cumulative fragment bypass
    High · 7.5 CVE-2026-9675 >= 8.0.0, < 8.5.0 8.5.0
  10. Undici has Unbounded Memory Consumption in WebSocket permessage-deflate Decompression
    High · 7.5 CVE-2026-1526 < 6.24.0, >= 7.0.0, < 7.24.0 6.24.0, 7.24.0
  11. Undici has Unhandled Exception in WebSocket Client Due to Invalid server_max_window_bits Validation
    High · 7.5 CVE-2026-2229 < 6.24.0, >= 7.0.0, < 7.24.0 6.24.0, 7.24.0
  12. Undici: Malicious WebSocket 64-bit length overflows parser and crashes the client
    High · 7.5 CVE-2026-1528 >= 6.0.0, < 6.24.0, >= 7.0.0, < 7.24.0 6.24.0, 7.24.0
  13. Regular Expression Denial of Service in Headers
    High · 7.5 CVE-2023-24807 < 5.19.1 5.19.1
  14. ProxyAgent vulnerable to MITM
    High · 7.7 CVE-2022-32210 >= 4.8.2, < 5.5.1 5.5.1

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