ADDITIONAL SYSTEM INFORMATION :
Tested on both Windows and Linux.

A DESCRIPTION OF THE PROBLEM :
In Java 24, CertificateFactory.generateCertificate was able to parse PEM files with trailing whitespace on the first line, which from what I understand is allowed by the spec.

However, in Java 25, the EOL character detection does not work properly and this results in an exception later on when the PEM parser is at the footer (see the "Actual result" section for the exception).

The bug seems to be on line 242 of Pem.java here: https://github.com/openjdk/jdk/blob/ef0851d8adbb834e1cd5aff5b3b973b953e57e2d/src/java.base/share/classes/sun/security/util/Pem.java#L242

From my understanding of the Pem.java code, the author intended to "skip" whitespace when determining the EOL char, like one would use a continue statement in a for loop or while loop. However, in reality, when whitespace is encountered in the switch statement, the code simply breaks out of it, and the eol variable will be equal to 0 rather than an actual EOL character.

This was handled correctly in Java 24, where the code would not break unless an actual newline was encountered: https://github.com/openjdk/jdk/blob/jdk-24%2B36/src/java.base/share/classes/sun/security/provider/X509Factory.java#L586-L612

REGRESSION : Last worked in version 24.0.2

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
See example source code

---------- BEGIN SOURCE ----------
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;

class PEMParserRegression {
    public static void main(String[] args) throws CertificateException {
        String pem = """
                -----BEGIN CERTIFICATE-----\s
                MIIFvjCCA6agAwIBAgIITyTh/u1bExowDQYJKoZIhvcNAQENBQAwYjEkMCIGA1UE
                CgwbRmluYW5zaWVsbCBJRC1UZWtuaWsgQklEIEFCMRowGAYDVQQLDBFJbmZyYXN0
                cnVjdHVyZSBDQTEeMBwGA1UEAwwVQmFua0lEIFNTTCBSb290IENBIHYxMB4XDTEx
                MTIwNzEyMzQwN1oXDTM0MTIzMTEyMzQwN1owYjEkMCIGA1UECgwbRmluYW5zaWVs
                bCBJRC1UZWtuaWsgQklEIEFCMRowGAYDVQQLDBFJbmZyYXN0cnVjdHVyZSBDQTEe
                MBwGA1UEAwwVQmFua0lEIFNTTCBSb290IENBIHYxMIICIjANBgkqhkiG9w0BAQEF
                AAOCAg8AMIICCgKCAgEAwVA4snZiSFI3r64LvYu4mOsI42A9aLKEQGq4IZo257iq
                vPH82SMvgBJgE52kCx7gQMmZ7iSm39CEA19hlILh8JEJNTyJNxMxVDN6cfJP1jMH
                JeTES1TmVbWUqGyLpyT8LCJhC9Vq4W3t/O1svGJNOUQIQL4eAHSvWTVoalxzomJh
                On97ENjXAt4BLb6sHfVBvmB5ReK0UfwpNACFM1RN8btEaDdWC4PfA72yzV3wK/cY
                5h2k1RM1s19PjoxnpJqrmn4qZmP4tN/nk2d7c4FErJAP0pnNsll1+JfkdMfiPD35
                +qcclpspzP2LpauQVyPbO21Nh+EPtr7+Iic2tkgz0g1kK0IL/foFrJ0Ievyr3Drm
                2uRnA0esZ45GOmZhE22mycEX9l7w9jrdsKtqs7N/T46hil4xBiGblXkqKNG6TvAR
                k6XqOp3RtUvGGaKZnGllsgTvP38/nrSMlszNojrlbDnm16GGoRTQnwr8l+Yvbz/e
                v/e6wVFDjb52ZB0Z/KTfjXOl5cAJ7OCbODMWf8Na56OTlIkrk5NyU/uGzJFUQSvG
                dLHUipJ/sTZCbqNSZUwboI0oQNO/Ygez2J6zgWXGpDWiN4LGLDmBhB3T8CMQu9J/
                BcFvgjnUyhyim35kDpjVPC8nrSir5OkaYgGdYWdDuv1456lFNPNNQcdZdt5fcmMC
                AwEAAaN4MHYwHQYDVR0OBBYEFPgqsux5RtcrIhAVeuLBSgBuRDFVMA8GA1UdEwEB
                /wQFMAMBAf8wHwYDVR0jBBgwFoAU+Cqy7HlG1ysiEBV64sFKAG5EMVUwEwYDVR0g
                BAwwCjAIBgYqhXBOAQQwDgYDVR0PAQH/BAQDAgEGMA0GCSqGSIb3DQEBDQUAA4IC
                AQAJOjUOS2GJPNrrrqf539aN1/EbUj5ZVRjG4wzVtX5yVqPGcRZjUQlNTcfOpwPo
                czKBnNX2OMF+Qm94bb+xXc/08AERqJJ3FPKu8oDNeK+Rv1X4nh95J4RHZcvl4AGh
                ECmGMyhyCea0qZBFBsBqQR7oC9afYOxsSovaPqX31QMLULWUYoBKWWHLVVIoHjAm
                GtAzMkLwe0/lrVyApr9iyXWhVr+qYGmFGw1+rwmvDmmSLWNWawYgH4NYxTf8z5hB
                iDOdAgilvyiAF8Yl0kCKUB2fAPhRNYlEcN+UP/KL24h/pB+hZ9mvR0tM6nW3HVZa
                DrvRz4VihZ8vRi3fYnOAkNE6kZdrrdO7LdBc9yYkfQdTcy0N+Aw7q4TkQ8npomrV
                mTKaPhtGhA7VICyRNBVcvyoxr+CY7aRQyHn/C7n/jRsQYxs7uc+msq6jRS4HPK8o
                lnF9usWZX6KY+8mweJiTE4uN4ZUUBUtt8WcXXDiK/bxEG2amjPcZ/b4LXwGCJb+a
                NWP4+iY6kBKrMANs01pLvtVjUS9RtRrY3cNEOhmKhO0qJSDXhsTcVtpbDr37UTSq
                QVw83dReiARPwGdURmmkaheH6z4k6qEUSXuFch0w53UAc+1aBXR1bgyFqMdy7Yxi
                b2AYu7wnrHioDWqP6DTkUSUeMB/zqWPM/qx6QNNOcaOcjA==
                -----END CERTIFICATE-----
                """;

        InputStream in = new ByteArrayInputStream(pem.getBytes());
        final CertificateFactory factory = CertificateFactory.getInstance("X.509");
        X509Certificate cert = (X509Certificate) factory.generateCertificate(in); // Throws exception since Java 25
        System.out.println(cert.getSubjectX500Principal().getName());
    }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Modify the PEM file to remove trailing whitespace on the first line

FREQUENCY :
ALWAYS