CVE-2007-1673 in Picozip
Summary
by MITRE
unzoo.c, as used in multiple products including AMaViS 2.4.1 and earlier, allows remote attackers to cause a denial of service (infinite loop) via a ZOO archive with a direntry structure that points to a previous file.
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Analysis
by VulDB Data Team • 08/02/2019
The vulnerability described in CVE-2007-1673 represents a critical denial of service flaw in the unzoo.c component that affects multiple software products including AMaViS version 2.4.1 and earlier. This issue stems from improper handling of ZOO archive structures during file extraction processes. The flaw specifically manifests when the direntry structure within a ZOO archive contains references that point to previous files in the archive, creating a circular reference condition that can lead to infinite loops during processing. This type of vulnerability falls under the category of improper input validation and can be classified as CWE-835, which deals with loops that do not contain a variable that is changed within the loop body. The vulnerability demonstrates a classic case of insufficient loop termination checking in archive processing routines.
The technical implementation of this vulnerability exploits the way the unzoo.c utility processes directory entries within ZOO archives. When encountering a direntry structure that references a previous file, the processing logic fails to detect the circular dependency and continues processing indefinitely. This creates a condition where the extraction process becomes trapped in a loop that never terminates, consuming system resources and making the affected service unavailable to legitimate users. The flaw is particularly dangerous because it can be triggered remotely through crafted ZOO archive files, making it an attractive target for attackers seeking to disrupt services. The vulnerability's impact is consistent with ATT&CK technique T1499.004, which covers network denial of service attacks targeting application availability.
The operational impact of CVE-2007-1673 extends beyond simple service disruption to potentially affect system stability and resource availability. When exploited, this vulnerability can cause the affected applications to consume excessive CPU cycles and memory resources, leading to system performance degradation or complete service unavailability. In environments where AMaViS or similar products handle email filtering or content scanning, this vulnerability could result in significant downtime and loss of email services. The remote exploitability of this flaw means that attackers do not need local access to the system to cause disruption, making it particularly concerning for networked environments. Organizations using affected versions should consider the potential for cascading effects when multiple services rely on the same vulnerable library components.
Mitigation strategies for CVE-2007-1673 should focus on both immediate remediation and long-term architectural improvements. The most effective immediate solution involves upgrading to patched versions of AMaViS and other affected software products that contain proper loop termination checks and circular reference detection. Organizations should also implement input validation measures that prevent processing of malformed ZOO archives, including implementing file size limits and archive structure validation. Network-level protections such as content filtering and sandboxing mechanisms can provide additional defense in depth. The vulnerability highlights the importance of proper error handling and input validation in archive processing libraries, as recommended by security frameworks like the OWASP Top Ten. Regular security assessments and vulnerability scanning should include checks for similar patterns in other archive processing components to prevent similar issues in the future.