TLS data modification via omitted Poly1305 verification
Published Feb 23, 2026 · Updated Feb 23, 2026
Cryptographic authentication bypass in Cesanta Mongoose 7.0 through 7.20 allows man-in-the-middle attackers to modify TLS data. The built-in TLS mg_chacha20_poly1305_decrypt function decrypts ChaCha20 ciphertext and returns plaintext without calculating or comparing its Poly1305 tag. Exploitation requires an in-path network position and a connection using the built-in ChaCha20-Poly1305 implementation; altered records are accepted as authentic.
Summary
What happened
Cryptographic authentication bypass in Cesanta Mongoose 7.0 through 7.20 allows man-in-the-middle attackers to modify TLS data. The built-in TLS mg_chacha20_poly1305_decrypt function decrypts ChaCha20 ciphertext and returns plaintext without calculating or comparing its Poly1305 tag. Exploitation requires an in-path network position and a connection using the built-in ChaCha20-Poly1305 implementation; altered records are accepted as authentic.
The record
- CVE
- CVE-2026-2968
- Published
- Feb 23, 2026
- Updated
- Feb 23, 2026
- Vendor
- Cesanta
- Product
- Mongoose
- Classifications
- CWE-347, CWE-345, T1557
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 23, 2026CVE publishedPublication date reported by the CVE source.
- Feb 23, 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=7.0
- Affected versionversion=7.1
- Affected versionversion=7.10
- Affected versionversion=7.11
- Affected versionversion=7.12
- Affected versionversion=7.13
- Affected versionversion=7.14
- Affected versionversion=7.15
- Affected versionversion=7.16
- Affected versionversion=7.17
- Affected versionversion=7.18
- Affected versionversion=7.19
- Affected versionversion=7.2
- Affected versionversion=7.20
- Affected versionversion=7.3
- Affected versionversion=7.4
- Affected versionversion=7.5
- Affected versionversion=7.6
- Affected versionversion=7.7
- Affected versionversion=7.8
- Affected versionversion=7.9
What conditions does exploitation require?
What is affected?
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
- Mongoose ChaCha20-Poly1305 authentication-bypass PoCproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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