# CVE-2021-29521: Segfault in SparseCountSparseOutput > An attacker can cause a segmentation fault and crash the application by providing a negative dense shape to the SparseCountSparseOutput operation. - **Severity:** Low 2.5 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 14 May 2021 - **Updated:** 3 Aug 2024 - **Also known as:** BIT-tensorflow-2021-29521, GHSA-hr84-fqvp-48mm, PYSEC-2021-158, PYSEC-2021-449, PYSEC-2021-647 ## What is CVE-2021-29521? CVE-2021-29521 is a low-severity denial of service vulnerability in Google Tensorflow, published on 14 May 2021. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description TensorFlow is an end-to-end open source platform for machine learning. Specifying a negative dense shape in `tf.raw_ops.SparseCountSparseOutput` results in a segmentation fault being thrown out from the standard library as `std::vector` invariants are broken. This is because the implementation(https://github.com/tensorflow/tensorflow/blob/8f7b60ee8c0206a2c99802e3a4d1bb55d2bc0624/tensorflow/core/kernels/count_ops.cc#L199-L213) assumes the first element of the dense shape is always positive and uses it to initialize a `BatchedMap` (i.e., `std::vector>`(https://github.com/tensorflow/tensorflow/blob/8f7b60ee8c0206a2c99802e3a4d1bb55d2bc0624/tensorflow/core/kernels/count_ops.cc#L27)) data structure. If the `shape` tensor has more than one element, `num_batches` is the first value in `shape`. Ensuring that the `dense_shape` argument is a valid tensor shape (that is, all elements are non-negative) solves this issue. The fix will be included in TensorFlow 2.5.0. We will also cherrypick this commit on TensorFlow 2.4.2 and TensorFlow 2.3.3. Weakness: CWE-131 (Incorrect Calculation of Buffer Size) ## Which versions are affected by CVE-2021-29521? 16 open source packages ship an affected version, including tensorflow, tensorflow-cpu and tensorflow-gpu. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `tensorflow` | Bitnami | From 2.3.0 | 2.3.3, 2.4.2 | | `tensorflow` | PyPI | From 2.3.0 | 2.3.3, 2.4.2 | | `tensorflow` | PyPI | From 2.3.0 | 2.3.3 | | `tensorflow` | PyPI | From 2.3.0 | 2.3.3 | | `tensorflow` | PyPI | From 2.4.0 | 2.4.2 | | `tensorflow` | PyPI | From 2.4.0 | 2.4.2 | | `tensorflow-cpu` | PyPI | From 2.3.0 | 2.3.3, 2.4.2 | | `tensorflow-cpu` | PyPI | From 2.3.0 | 2.3.3 | | `tensorflow-cpu` | PyPI | From 2.3.0 | 2.3.3 | | `tensorflow-cpu` | PyPI | From 2.4.0 | 2.4.2 | | `tensorflow-cpu` | PyPI | From 2.4.0 | 2.4.2 | | `tensorflow-gpu` | PyPI | From 2.3.0 | 2.3.3, 2.4.2 | | `tensorflow-gpu` | PyPI | From 2.3.0 | 2.3.3 | | `tensorflow-gpu` | PyPI | From 2.3.0 | 2.3.3 | | `tensorflow-gpu` | PyPI | From 2.4.0 | 2.4.2 | | `tensorflow-gpu` | PyPI | From 2.4.0 | 2.4.2 | Products: Google Tensorflow. ## How do I fix CVE-2021-29521? Upgrade tensorflow to a fixed version for your release line: 2.3.3 or 2.4.2. ## Is CVE-2021-29521 being exploited? There is no known exploitation of CVE-2021-29521 in the wild and no public exploit code. ## Other vulnerabilities in Google Tensorflow - [CVE-2023-25668](https://insights.sbomify.com/CVE-2023-25668/): TensorFlow vulnerable to heap out-of-buffer read in the QuantizeAndDequantize operation (critical 9.8) - [CVE-2018-7575](https://insights.sbomify.com/CVE-2018-7575/): Integer Overflow or Wraparound in Google TensorFlow (critical 9.8) - [CVE-2021-37678](https://insights.sbomify.com/CVE-2021-37678/): Arbitrary code execution due to YAML deserialization (critical 9.3) - [CVE-2021-35958](https://insights.sbomify.com/CVE-2021-35958/): Path traversal in n/a (critical 9.1) - [CVE-2020-15202](https://insights.sbomify.com/CVE-2020-15202/): Integer truncation in Shard API usage (critical 9.0) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-29521 and fix it if it is affected. What it is: CVE-2021-29521 is a low-severity denial of service vulnerability in Google Tensorflow, published on 14 May 2021. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2021-29521 in the wild and no public exploit code. Affected packages and fixed versions: - tensorflow (Bitnami): affected from 2.3.0; fixed in 2.3.3, 2.4.2 - tensorflow (PyPI): affected from 2.3.0; fixed in 2.3.3, 2.4.2 - tensorflow (PyPI): affected from 2.3.0; fixed in 2.3.3 - tensorflow (PyPI): affected from 2.3.0; fixed in 2.3.3 - tensorflow (PyPI): affected from 2.4.0; fixed in 2.4.2 - tensorflow (PyPI): affected from 2.4.0; fixed in 2.4.2 - tensorflow-cpu (PyPI): affected from 2.3.0; fixed in 2.3.3, 2.4.2 - tensorflow-cpu (PyPI): affected from 2.3.0; fixed in 2.3.3 - tensorflow-cpu (PyPI): affected from 2.3.0; fixed in 2.3.3 - tensorflow-cpu (PyPI): affected from 2.4.0; fixed in 2.4.2 - tensorflow-cpu (PyPI): affected from 2.4.0; fixed in 2.4.2 - tensorflow-gpu (PyPI): affected from 2.3.0; fixed in 2.3.3, 2.4.2 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2021-29521/ (Markdown: https://insights.sbomify.com/CVE-2021-29521/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-29521 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-29521 - OSV: https://osv.dev/vulnerability/CVE-2021-29521 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-29521/ Summaries are generated and may contain mistakes; the official description above is the record.