undici vulnerable to cookie attribute injection via unsanitized domain and unparsed setCookie fields

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undici's setCookie function does not fully sanitize cookie attributes. In undici before 6.28.0, from 7.0.0 up to before 7.29.0, and from 8.0.0 up to before 8.9.0, a domain value is not checked for semicolons and entries in the unparsed array are not sanitized, so attacker-influenced input can inject additional cookie attributes. For example, a domain value containing a semicolon can append attributes such as SameSite, and an unparsed entry can inject attributes such as HttpOnly, without the caller setting them. Applications that pass user-controlled input to these fields, such as multi-tenant or reverse-proxy servers that scope session cookies to a tenant-supplied domain, can have SameSite CSRF protections bypassed, or the Secure, HttpOnly, and SameSite attributes forced, stripped, or overridden. The issue is fixed in undici 6.28.0, 7.29.0, and 8.9.0.

Source published

29 Jul 2026 16:45:57 UTC

Source modified

29 Jul 2026 18:08:16 UTC

Saved here

23 Oct 2026 15:48:27 UTC

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CVE Program Terms of Use

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CVSS 3.1 · 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

undici's setCookie function does not fully sanitize cookie attributes. In undici before 6.28.0, from 7.0.0 up to before 7.29.0, and from 8.0.0 up to before 8.9.0, a domain value is not checked for semicolons and entries in the unparsed array are not sanitized, so attacker-influenced input can inject additional cookie attributes. For example, a domain value containing a semicolon can append attributes such as SameSite, and an unparsed entry can inject attributes such as HttpOnly, without the caller setting them. Applications that pass user-controlled input to these fields, such as multi-tenant or reverse-proxy servers that scope session cookies to a tenant-supplied domain, can have SameSite CSRF protections bypassed, or the Secure, HttpOnly, and SameSite attributes forced, stripped, or overridden. The issue is fixed in undici 6.28.0, 7.29.0, and 8.9.0.

Source published

Jul 29, 2026, 4:45:57 PM (timezone not stated)

Source modified

Jul 29, 2026, 6:08:16 PM (timezone not stated)

Saved here

15 Nov 2026 07:33:03 UTC

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ENISA EUVD · source terms and attribution apply

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Source: euvd · ENISA EUVD · source terms and attribution apply. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

EUVD CVSS 3.1 · 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

undici's setCookie function does not fully sanitize cookie attributes. In undici before 6.28.0, from 7.0.0 up to before 7.29.0, and from 8.0.0 up to before 8.9.0, a domain value is not checked for semicolons and entries in the unparsed array are not sanitized, so attacker-influenced input can inject additional cookie attributes. For example, a domain value containing a semicolon can append attributes such as SameSite, and an unparsed entry can inject attributes such as HttpOnly, without the caller setting them. Applications that pass user-controlled input to these fields, such as multi-tenant or reverse-proxy servers that scope session cookies to a tenant-supplied domain, can have SameSite CSRF protections bypassed, or the Secure, HttpOnly, and SameSite attributes forced, stripped, or overridden. The issue is fixed in undici 6.28.0, 7.29.0, and 8.9.0.

Source published

29 Jul 2026 17:16:51 UTC

Source modified

5 Aug 2026 15:18:55 UTC

Saved here

25 Oct 2026 05:17:25 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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CVSS 3.1 · ce714d77-add3-4f53-aff5-83d477b104bb · Secondary · 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

CVSS 3.1 · [email protected] · Primary · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

## Impact The `setCookie` function has two attribute injection paths. `validateCookieDomain` does not reject semicolons (`validateCookiePath` already does at 0x3B), so a `domain` value like `example.com; SameSite=None` lands verbatim as `Domain=example.com; SameSite=None`. The `unparsed` array's loop only checks each entry contains `=` and does not sanitize values, so an entry like `X-Custom=val; HttpOnly` lands unchanged, injecting `HttpOnly` without the caller setting `cookie.httpOnly = true`. Applications that pass user-controlled input to these fields, typically multi-tenant or reverse-proxy servers that scope session cookies to a tenant-supplied domain, can have SameSite CSRF protections bypassed, `Secure` or `HttpOnly` forced or stripped, or the intended SameSite tier overridden. ## Patches Patched in undici v6.28.0, v7.29.0, and v8.9.0. ## Workarounds - Sanitize `domain` values against the RFC 1034 letter-digit-hyphen set before passing to `setCookie`. - Do not pass user-controlled data to the `unparsed` field.

Source published

3 Aug 2026 19:30:52 UTC

Source modified

10 Sep 2026 03:51:14 UTC

Saved here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Publisher rating · MODERATE