Impact
X.509 certificates can identify elliptic curves using either an object identifier or using explicit encoding of the parameters.
An attacker could present an ECDSA X.509 certificate using explicit encoding where the parameters are very large. The POC used a 16Kbit prime for this purpose. When parsing the parameter is checked to be prime, causing excessive computation.
Patches
This was patched in 2.19.4 and 3.3.0 to allow the prime parameter of the elliptic curve to be at most 521 bits.
Workarounds
None known.
Other Notes
Support for explicit encoding of elliptic curve parameters is deprecated in Botan.
Credit
Reported by Bing Shi
Impact
X.509 certificates can identify elliptic curves using either an object identifier or using explicit encoding of the parameters.
An attacker could present an ECDSA X.509 certificate using explicit encoding where the parameters are very large. The POC used a 16Kbit prime for this purpose. When parsing the parameter is checked to be prime, causing excessive computation.
Patches
This was patched in 2.19.4 and 3.3.0 to allow the prime parameter of the elliptic curve to be at most 521 bits.
Workarounds
None known.
Other Notes
Support for explicit encoding of elliptic curve parameters is deprecated in Botan.
Credit
Reported by Bing Shi