Software Update: PuTTY 0.63 Beta

A new beta release of PuTTY has been released, version 0.63. PuTTY is one of the most popular telnet and ssh clients, which makes it possible to remotely manage a computer over a secure connection. Originally, the program was only available for Windows, but now there are also clients for the various Unix platforms. In version 0.63 we find several bug fixes and four security vulnerabilities have been fixed.

sPuTTY 0.63 released, fixing SECURITY HOLES

PuTTY 0.63 fixes four security holes in 0.62 and before: vuln-modmul, vuln-signature-stringlen, vuln-bignum-division-by-zero, private-key-not-wiped. Other than that, there are mostly bug fixes from 0.62 and a few small features.

These features are new in beta 0.63:

  • Security fix: prevent a nefarious SSH server or network attacker from crashing PuTTY at startup in three different ways by presenting a maliciously constructed public key and signature.
  • Security fix: PuTTY no longer retains the private half of users’ keys in memory by mistake after authenticating with them.
  • Revamped the internal configuration storage system to remove all fixed arbitrary limits on string lengths. In particular, there should now no longer be an unreasonably small limit on the number of port forwardings PuTTY can store.
  • Port-forwarded TCP connections which close one direction before the other should now be reliably supported, with EOF propagated independently in the two directions. This also fixes some instances of port-forwarding data corruption (if the corruption consisted of losing data from the very end of the connection) and some instances of PuTTY failing to close when the session is over (because it wrongly thought a forwarding channel was still active when it was not).
  • The terminal emulation now supports xterm’s bracketed paste mode (allowing aware applications to tell the difference between typed and pasted text, so that eg editors need not apply inappropriate auto-indent).
  • You can now choose to display bold text by both brightening the foreground color and changing the font, not just one or the other.
  • PuTTYgen will now never generate a 2047-bit key when asked for 2048 (or more generally n-1 bits when asked for n).
  • Some updates to default settings: PuTTYgen now generates 2048-bit keys by default (rather than 1024), and PuTTY defaults to UTF-8 encoding and 2000 lines of scrollback (rather than ISO 8859-1 and 200).
  • Unix: PSCP and PSFTP now preserve the Unix file permissions, on copies in both directions.
  • Unix: dead keys and compose-character sequences are now supported.
  • Unix: PuTTY and pterm now permit font fallback (where glyphs not present in your selected font are automatically filled in from other fonts on the system) even if you are using a server-side X11 font rather than a Pango client-side one.
  • Bug fixes too numerous to list, mostly resulting from running the code through Coverity Scan which spotted an assortment of memory and resource leaks, logic errors, and crashes in various circumstances.

Version number 0.63 beta
Release status beta
Operating systems Windows 7, Linux, Windows XP, Windows Server 2003, Windows Vista, Windows Server 2008, Windows Server 2012, Windows 8
Website putty
File size


License type GPL