gpg in GnuPG before 1.4.2.2 does not properly verify non-detached signatures, which allows attackers to inject unsigned data via a data packet that is not associated with a control packet, which causes the check for concatenated signatures to report that the signature is valid, a different vulnerability than CVE-2006-0455.

Tavis Ormandy noticed that gnupg, the GNU privacy guard - a free PGP replacement, can be tricked to emit a 'good signature' status message when a valid signature is included which does not belong to the data packet. This update basically adds fixed packages for woody whose version turned out to be vulnerable as well.

An updated GnuPG package that fixes signature verification flaws as well as minor bugs is now available.

This update has been rated as having important security impact by the Red Hat Security Response Team.

GnuPG is a utility for encrypting data and creating digital signatures.

Tavis Ormandy discovered a bug in the way GnuPG verifies cryptographically signed data with detached signatures. It is possible for an attacker to construct a cryptographically signed message which could appear to come from a third party. When a victim processes a GnuPG message with a malformed detached signature, GnuPG ignores the malformed signature, processes and outputs the signed data, and exits with status 0, just as it would if the signature had been valid. In this case, GnuPG's exit status would not indicate that no signature verification had taken place. This issue would primarily be of concern when processing GnuPG results via an automated script. The Common Vulnerabilities and Exposures project assigned the name CVE-2006-0455 to this issue.

Tavis Ormandy also discovered a bug in the way GnuPG verifies cryptographically signed data with inline signatures. It is possible for an attacker to inject unsigned data into a signed message in such a way that when a victim processes the message to recover the data, the unsigned data is output along with the signed data, gaining the appearance of having been signed. This issue is mitigated in the GnuPG shipped with Red Hat Enterprise Linux as the --ignore-crc-error option must be passed to the gpg executable for this attack to be successful.
The Common Vulnerabilities and Exposures project assigned the name CVE-2006-0049 to this issue.

Please note that neither of these issues affect the way RPM or up2date verify RPM package files, nor is RPM vulnerable to either of these issues.

All users of GnuPG are advised to upgrade to this updated package, which contains backported patches to correct these issues.

Werner Koch reports :

In the aftermath of the false positive signature verfication bug (announced 2006-02-15) more thorough testing of the fix has been done and another vulnerability has been detected. This new problem affects the use of *gpg* for verification of signatures which are _not_ detached signatures. The problem also affects verification of signatures embedded in encrypted messages; i.e. standard use of gpg for mails.

Tavis Ormandy discovered a flaw in gnupg's signature verification. In some cases, certain invalid signature formats could cause gpg to report a 'good signature' result for auxiliary unsigned data which was prepended or appended to the checked message part.

Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Another vulnerability, different from that fixed in MDKSA-2006:043 (CVE-2006-0455), was discovered in gnupg in the handling of signature files.

This vulnerability is corrected in gnupg 1.4.2.2 which is being provided with this update.

The remote Redhat Enterprise Linux 4 host has a package installed that is affected by multiple vulnerabilities as referenced in the RHSA-2006:0266 advisory.

  - security flaw (CVE-2006-0049, CVE-2006-0455)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Tavis Ormandy discovered a flaw in the way GnuPG verifies cryptographically signed data with inline signatures. It is possible for an attacker to add unsigned text to a signed message in such a way so that when the signed text is extracted, the unsigned text is extracted as well, appearing as if it had been signed. The Common Vulnerabilities and Exposures project assigned the name CVE-2006-0049 to this issue.

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

New GnuPG packages are available for Slackware 9.0, 9.1, 10.0, 10.1, 10.2, and -current to fix security issues.

The remote host is affected by the vulnerability described in GLSA-200603-08 (GnuPG: Incorrect signature verification)

    OpenPGP is the standard that defines the format of digital     signatures supported by GnuPG. OpenPGP signatures consist of multiple     sections, in a strictly defined order. Tavis Ormandy of the Gentoo     Linux Security Audit Team discovered that certain illegal signature     formats could allow signed data to be modified without detection. GnuPG     has previously attempted to be lenient when processing malformed or     legacy signature formats, but this has now been found to be insecure.
  Impact :

    A remote attacker may be able to construct or modify a     digitally-signed message, potentially allowing them to bypass     authentication systems, or impersonate another user.
  Workaround :

    There is no known workaround at this time.

ID	Name	Product	Family	Severity
22859	Debian DSA-993-2 : gnupg - programming error	Nessus	Debian Local Security Checks	medium
21990	CentOS 3 / 4 : gnu / gnupg (CESA-2006:0266)	Nessus	CentOS Local Security Checks	medium
21478	FreeBSD : GnuPG does not detect injection of unsigned data (948921ad-afbc-11da-bad9-02e081235dab)	Nessus	FreeBSD Local Security Checks	medium
21182	Ubuntu 4.10 / 5.04 / 5.10 : gnupg vulnerability (USN-264-1)	Nessus	Ubuntu Local Security Checks	medium
21098	Mandrake Linux Security Advisory : gnupg (MDKSA-2006:055)	Nessus	Mandriva Local Security Checks	medium
21090	RHEL 4 : gnupg (RHSA-2006:0266)	Nessus	Red Hat Local Security Checks	high
21076	Fedora Core 4 : gnupg-1.4.2.2-1 (2006-147)	Nessus	Fedora Local Security Checks	medium
21075	Slackware 10.0 / 10.1 / 10.2 / 9.0 / 9.1 / current : gnupg (SSA:2006-072-02)	Nessus	Slackware Local Security Checks	medium
21046	GLSA-200603-08 : GnuPG: Incorrect signature verification	Nessus	Gentoo Local Security Checks	medium

Detections

Analytics

CVE-2006-0049

high

Tenable Plugins

medium

medium

medium

medium

medium

high

medium

medium

medium