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Details on the GnuPG 1.4.15 and 2.0.22 release

Taylor asked me to forward this background info:

On Sat, 5 Oct 2013 10:56, said:
> not yet been seen in the wild. Details of the attack will eventually
> be published by its inventor.

The zlib compression language that OpenPGP uses is powerful enough to
express an OpenPGP compression quine -- that is, an OpenPGP compressed
data packet that decompresses to itself -- causing infinite nesting of
OpenPGP packets. Source code to generate such a quine is at

When fed the quine, older versions of GnuPG would blow the stack and
crash. GnuPG 1.4.15 and GnuPG 2.0.22 avoid this by setting a small
constant bound on the depth of packet nesting.

(This is similar to Tavis Ormandy's IPcomp compression quine, reported
in CVE-2011-1547, which I didn't know about at the time I made the
OpenPGP compression quine. Both of us had read Russ Cox's article on
zlib compression quines: <>.)



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