Bug 2555865 (CVE-2026-112396)

Summary: CVE-2026-112396 pillow: pillow: arbitrary code execution via heap use-after-free during TIFF encoding
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: alinfoot, anpicker, anthomas, aprice, bbrownin, cmyers, dfreiber, dnakabaa, doconnor, drow, dschmidt, dtrifiro, ebourniv, ehelms, ggainey, hasun, ilpinto, jburrell, jfula, jlanda, jmitchel, jowilson, jpasqual, jsamir, juwatts, jwong, kaycoth, kshier, lcouzens, ltomasbo, mdellweg, mhayden, mhulan, mwoodson, nmoumoul, nyancey, oezr, omaciel, ometelka, osousa, pcreech, ptisnovs, rbobbitt, rchan, rhel-process-autobot, sbunciak, sdoran, simaishi, smallamp, stcannon, syedriko, tmalecek, vkumar, watson-tool-maintainers, weaton, xdharmai, yguenane, ykashtan
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Pillow. This vulnerability allows a remote attacker to potentially execute arbitrary code or cause a Denial of Service (DoS). The issue occurs when an application encodes Tagged Image File Format (TIFF) data with untrusted tags into an in-memory buffer. When an invalid tag is rejected during encoding, improper error handling prematurely frees memory that is subsequently accessed during cleanup, triggering a heap use-after-free condition.
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Description OSIDB Bzimport 2026-10-19 21:22:11 UTC 
Pillow is a Python imaging library. From 11.3.0 until 13.0.0, Pillow has a heap use-after-free when libtiff rejects a tag while encoding TIFF data to an in-memory buffer. When an application saves attacker-influenced TIFF tags to BytesIO, libtiff can reject a tag during encoding in ImagingLibTiffEncode; the error path then frees the output buffer without closing or clearing the TIFF handle, and later cleanup flushes through the write callback into freed memory, which can crash the process and may enable code execution. This issue is fixed in version 13.0.0.