CVE intelligence and bounded remediation

CVE-2019-1543 — ChaCha20-Poly1305 is an AEAD cipher, and requires a unique nonce input for every encryption operation

High CVSS 7.4

ChaCha20-Poly1305 is an AEAD cipher, and requires a unique nonce input for every encryption operation. RFC 7539 specifies that the nonce value (IV) should be 96 bits (12 bytes). OpenSSL allows a variable nonce length and front pads the nonce with 0 bytes if it is less than 12 bytes. However it also incorrectly allows a nonce to be set of up to 16 bytes. In this case only the last 12 bytes are significant and any additional leading bytes are ignored. It is a requirement of using this cipher that nonce values are unique. Messages encrypted using a reused nonce value are susceptible to serious confidentiality and integrity attacks. If an application changes the default nonce length to be longer than 12 bytes and then makes a change to the leading bytes of the nonce expecting the new value to be a new unique nonce then such an application could inadvertently encrypt messages with a reused nonce. Additionally the ignored bytes in a long nonce are not covered by the integrity guarantee of this cipher. Any application that relies on the integrity of these ignored leading bytes of a long nonce may be further affected. Any OpenSSL internal use of this cipher, including in SSL/TLS, is safe…

Severity
High
CVSS
7.4 (3.0)
Published
2019-03-06
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-327, CWE-330

Affected products

  • openssl / openssl

Showing 1 representative product identities from 2 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Cryptography, certificate, signature, and channel validation

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Check exposure

  • Inventory affected algorithms, key uses, trust stores, certificate validation settings, random sources, and plaintext channels across clients and services.
  • Determine which secrets, identities, signatures, or data protections depend on the affected primitive or validation path.
  • Check debug, compatibility, fallback, and hostname or audience override settings in build and runtime configuration.

Remediate safely

  • Use a maintained platform cryptographic API with approved algorithms, modes, parameters, randomness, and full peer identity validation.
  • Remove insecure fallback and validation bypasses; separate keys by purpose and load them from managed secret storage.
  • Plan rotation or reissuance for affected keys, certificates, tokens, hashes, or ciphertext and document compatibility sequencing.

Authoritative sources

Complete CVE record and remediation plan

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