Summary
Workarounds
Use any version but affected versions: >= 10.3.0, < 12.2.0
Resources
- Fix: https://github.com/python-pillow/Pillow/pull/9520
- Original issue: CVE-2026-25990 (Pillow 12.1.1)
Impact
Processing a malicious PSD file could lead to memory corruption, potentially resulting in a crash or arbitrary code execution.
An arithmetic operation produces a value that exceeds the integer type's maximum, causing it to wrap to an unexpected small value. Typical impact: incorrect size calculations leading to heap overflows or logic errors.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
Patched version: 12.2.0
Pillow 12.1.1 addressed CVE-2026-25990 by adding checks for tile extents in PSD image decoding/encoding to prevent an out-of-bounds write. However, the bounds checks computed tile extent sums using types susceptible to integer overflow, meaning a PSD image with carefully chosen tile dimensions could produce values that wrap around and bypass the checks, still triggering an out-of-bounds write in src/decode.c and src/encode.c. The fix avoids adding extents together before comparison.
Frequently Asked Questions
- What is CVE-2026-42311? CVE-2026-42311 is a high-severity integer overflow or wraparound vulnerability in pillow (pip), affecting versions >= 10.3.0, < 12.2.0. It is fixed in 12.2.0. An arithmetic operation produces a value that exceeds the integer type's maximum, causing it to wrap to an unexpected small value.
- Which versions of pillow are affected by CVE-2026-42311? pillow (pip) versions >= 10.3.0, < 12.2.0 is affected.
- Is there a fix for CVE-2026-42311? Yes. CVE-2026-42311 is fixed in 12.2.0. Upgrade to this version or later.
- Is CVE-2026-42311 exploitable, and should I be worried? Whether CVE-2026-42311 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-42311 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-42311? Upgrade
pillowto 12.2.0 or later.