Unable to apply errata EN-26:15 (OpenSSL)

I'm trying to apply errata EN-26:15 on a 15.0 fresh tree, with all other erratas and advisories already applied except SA-26:35 (also OpenSSL related, which seems to depend on EN-26:15). Using patch --dry-run < ... I'm getting some errors when target file is "+++/dev/null" (first file concerned is crypto/openssl/util/check-format-commit.sh.orig). I checked the patch signature. Any idea ??