Cookie attribute injection via unsanitized ResponseCookie fields
Published Sep 15, 2026 · Updated Sep 15, 2026
Cookie injection in http4s before 0.23.35 and 1.0.0-M1 through 1.0.0-M46 allows attackers to alter Set-Cookie attributes. ResponseCookie.render writes attacker-influenced name, content, domain, path, and extension values without removing semicolons or control characters. The application must build a ResponseCookie from unvalidated input; injected attributes can widen cookie scope or weaken protections, while permissive backends can split headers.
Summary
What happened
Cookie injection in http4s before 0.23.35 and 1.0.0-M1 through 1.0.0-M46 allows attackers to alter Set-Cookie attributes. ResponseCookie.render writes attacker-influenced name, content, domain, path, and extension values without removing semicolons or control characters. The application must build a ResponseCookie from unvalidated input; injected attributes can widen cookie scope or weaken protections, while permissive backends can split headers.
The record
- CVE
- CVE-2026-69211
- Published
- Sep 15, 2026
- Updated
- Sep 15, 2026
- Vendor
- http4s
- Product
- http4s
- Classifications
- Unavailable
- Attack vector
- network
- Privileges
- Unavailable
Timeline
How it unfolded
- Sep 15, 2026CVE publishedPublication date reported by the CVE source.
- Sep 15, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 0.23.35
- Affected versionversion=>= 1.0.0-M1, < 1.0.0-M47
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
No sourced classifications are available.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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