CVE-2020-15211

Vulnerability Description

In TensorFlow Lite before versions 1.15.4, 2.0.3, 2.1.2, 2.2.1 and 2.3.1, saved models in the flatbuffer format use a double indexing scheme: a model has a set of subgraphs, each subgraph has a set of operators and each operator has a set of input/output tensors. The flatbuffer format uses indices for the tensors, indexing into an array of tensors that is owned by the subgraph. This results in a pattern of double array indexing when trying to get the data of each tensor. However, some operators can have some tensors be optional. To handle this scenario, the flatbuffer model uses a negative `-1` value as index for these tensors. This results in special casing during validation at model loading time. Unfortunately, this means that the `-1` index is a valid tensor index for any operator, including those that don't expect optional inputs and including for output tensors. Thus, this allows writing and reading from outside the bounds of heap allocated arrays, although only at a specific offset from the start of these arrays. This results in both read and write gadgets, albeit very limited in scope. The issue is patched in several commits (46d5b0852, 00302787b7, e11f5558, cd31fd0ce, 1970c21, and fff2c83), and is released in TensorFlow versions 1.15.4, 2.0.3, 2.1.2, 2.2.1, or 2.3.1. A potential workaround would be to add a custom `Verifier` to the model loading code to ensure that only operators which accept optional inputs use the `-1` special value and only for the tensors that they expect to be optional. Since this allow-list type approach is erro-prone, we advise upgrading to the patched code.

CVSS Score

Affected Products

Related Weaknesses (CWE)

References

• http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00065.htmlMailing ListThird Party Advisory
• https://github.com/tensorflow/tensorflow/commit/00302787b788c5ff04cb6f62aed5a74dPatchThird Party Advisory
• https://github.com/tensorflow/tensorflow/commit/1970c2158b1ffa416d159d03c3370b9aPatchThird Party Advisory
• https://github.com/tensorflow/tensorflow/commit/46d5b0852528ddfd614ded79bccc7558PatchThird Party Advisory
• https://github.com/tensorflow/tensorflow/commit/cd31fd0ce0449a9e0f83dcad08d6ed7fPatchThird Party Advisory
• https://github.com/tensorflow/tensorflow/commit/e11f55585f614645b360563072ffeb5cPatchThird Party Advisory
• https://github.com/tensorflow/tensorflow/commit/fff2c8326280c07733828f990548979bPatchThird Party Advisory
• https://github.com/tensorflow/tensorflow/releases/tag/v2.3.1Third Party Advisory
• https://github.com/tensorflow/tensorflow/security/advisories/GHSA-cvpc-8phh-8f45ExploitThird Party Advisory
• http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00065.htmlMailing ListThird Party Advisory
• https://github.com/tensorflow/tensorflow/commit/00302787b788c5ff04cb6f62aed5a74dPatchThird Party Advisory
• https://github.com/tensorflow/tensorflow/commit/1970c2158b1ffa416d159d03c3370b9aPatchThird Party Advisory
• https://github.com/tensorflow/tensorflow/commit/46d5b0852528ddfd614ded79bccc7558PatchThird Party Advisory
• https://github.com/tensorflow/tensorflow/commit/cd31fd0ce0449a9e0f83dcad08d6ed7fPatchThird Party Advisory
• https://github.com/tensorflow/tensorflow/commit/e11f55585f614645b360563072ffeb5cPatchThird Party Advisory