Adobe promises patch for seven-month old Flash flaw

Vendor knew about critical vulnerability in December 2008, never fixed it, slates updates for late next week

Adobe Systems Inc. late Wednesday admitted its Flash and Reader software have a critical vulnerability and promised it would patch both next week.

One security researcher, however, said Adobe's own bug-tracking database shows that the company has known of the vulnerability for nearly seven months.

In a security advisory posted around 10 p.m. Eastern time Wednesday, Adobe acknowledged that earlier reports were on target. "A critical vulnerability exists in the current versions of Flash Player (v9.0.159.0 and v10.0.22.87) for Windows, Macintosh and Linux operating systems, and the authplay.dll component that ships with Adobe Reader and Acrobat v9.x for Windows, Macintosh and UNIX operating systems," the company said.

The "authplay.dll" mentioned in the advisory is the interpreter that handles Flash content embedded within PDF files, and is present on any machine equipped with Reader and Acrobat.

Adobe said it would patch all versions of Flash by July 30, and Reader and Acrobat for Windows and Mac no later than July 31. Until a patch is available, Adobe said users could delete or rename authplay.dll, or disable Flash rendering to stymie attacks within malformed PDF files. Adobe did not offer any similar workaround for Flash and could only recommend that "users should exercise caution in browsing untrusted websites."

The U.S. Computer Emergency Response Team (US-CERT), part of the Department of Homeland Security, included instructions on how to delete the Flash interpreter from Windows, Mac and Linux machines in a Wednesday advisory of its own.

Unlike previous PDF-based attacks, disabling the application's use of JavaScript does no good. Firefox users can install the NoScript add-on to block Flash directed at the browser, and Windows Vista users are shielded from silent attacks by the operating system's User Account Control (UAC) prompts.

While Adobe stopped short in its advisory and an accompanying blog post of confirming attacks, more security companies stepped forward Wednesday to report they had spotted not only hacks using rigged PDF documents, but also drive-by attacks launched from compromised Web sites.

Most attacks reported so far have been exploits served by malicious PDF files. "The PDF here is just the vehicle for the attack," explained Marc Rossi, the manager of development at Symantec. In those cases, the exploit relies on the flawed authplay.dll installed with Reader. "But it's not like you need to have both Flash and Reader on your system," added Rossi. "The possibility definitely exists that a malicious Flash stream from a Web site could exploit this."

That's exactly what others are reporting. Mid-day Wednesday, Paul Royal, a principal researcher at Purewire, said in an e-mail that he had found multiple malicious sites serving up Flash-based attacks. Later in the day, SANS' Internet Storm Center (ISC) echoed Royal. "We [have] confirmed that the links have been injected in legitimate web sites to create a drive-by attack, as expected," ISC handler Bojan Zdrnja said in a warning on the center's site.

Exploits remain few in number, but Rossi expected them to ramp up quickly. "We're seeing very limited exploitation so far, which is pretty typical. PDF attacks tend to start out as targeted e-mail attacks, with an [poisoned] attachment, directed at specific people." After the exploit gains access to the PC -- all in-the-wild attacks seen so far target Windows machines -- it "phones home" to a Web site, Rossi said, to download a Trojan onto the compromised system.

Purewire's Royal noticed that the flaw in Flash was first logged into Adobe's bug-tracking database Dec. 31, 20008, but the current exploit code appears to have been crafted much more recently, on July 9. It's possible that attacks have been in circulation since then. "The bug has apparently existed since December 2008," Royal said.

Although Adobe blocked access to the bug's page for several hours Wednesday night, it reopened the page by about 1 a.m. Eastern today. As Royal reported, the "Created" date for the bug was listed as "12/31/08" on the Adobe Flash Player Bug and Issue Management System.

Adobe has been under the security microscope this week. On Monday, Danish bug tracker Secunia noticed that Adobe continues to provide an outdated edition of Reader for download from its Web site, a practice Adobe originally defended as necessary to produce patches quickly. Tuesday, however, Adobe said it was reevaluating Reader's updating process to close the exploit window.

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Gregg Keizer

Gregg Keizer

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