CVE-2023-34095

cpdb-libs provides frontend and backend libraries for the Common Printing Dialog Backends (CPDB) project. In versions 1.0 through 2.0b4, cpdb-libs is vulnerable to buffer overflows via improper use of scanf(3). cpdb-libs uses the fscanf() and scanf() functions to parse command lines and configuration files, dropping the read string components into fixed-length buffers, but does not limit the length of the strings to be read by fscanf() and scanf() causing buffer overflows when a string is longer than 1023 characters. A patch for this issue is available at commit f181bd1f14757c2ae0f17cc76dc20421a40f30b7. As all buffers have a length of 1024 characters, the patch limits the maximum string length to be read to 1023 by replacing all occurrences of %s with %1023s in all calls of the fscanf() and scanf() functions.

Weakness

A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

Affected Software

Potential Mitigations

• Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.
• D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.
• Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.
• Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.
• For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

References

• http://www.openwall.com/lists/oss-security/2023/06/14/7
• https://github.com/OpenPrinting/cpdb-libs/blob/85555fba64d34f53a2fce099b0488904cc48ed35/cpdb/cpdb-frontend.c#L372
• https://github.com/OpenPrinting/cpdb-libs/blob/85555fba64d34f53a2fce099b0488904cc48ed35/tools/cpdb-text-frontend.c#L362
• https://github.com/OpenPrinting/cpdb-libs/blob/85555fba64d34f53a2fce099b0488904cc48ed35/tools/cpdb-text-frontend.c#L453
• https://github.com/OpenPrinting/cpdb-libs/commit/f181bd1f14757c2ae0f17cc76dc20421a40f30b7
• https://github.com/OpenPrinting/cpdb-libs/security/advisories/GHSA-25j7-9gfc-f46x