Session forgery via empty default HMAC key
Published Aug 22, 2026 · Updated Aug 22, 2026
Session integrity failure in Robert Acock Punk before 0.18 allows remote attackers to forge signed session cookies without authentication. The session keyword freezes an absent, undefined, or empty secret, and cookie reads and writes then use a zero-length HMAC-SHA256 key. An attacker who knows the cookie format can mint valid cookies offline and assume any identity or role stored in the session.
Summary
What happened
Session integrity failure in Robert Acock Punk before 0.18 allows remote attackers to forge signed session cookies without authentication. The session keyword freezes an absent, undefined, or empty secret, and cookie reads and writes then use a zero-length HMAC-SHA256 key. An attacker who knows the cookie format can mint valid cookies offline and assume any identity or role stored in the session.
The record
- CVE
- CVE-2026-75870
- Published
- Aug 22, 2026
- Updated
- Aug 22, 2026
- Vendor
- Robert Acock
- Product
- Punk
- Classifications
- T1606.001
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 22, 2026CVE publishedPublication date reported by the CVE source.
- Aug 22, 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 <0.18
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
Public exploit references
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Technologies
Your stack
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Your stack
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