What is CVE-2021-29521?

CVE-2021-29521 is a low-severity vulnerability in Google Tensorflow, classified under Incorrect Calculation of Buffer Size. CVSS score: 2.5/10. Published 2021-05-14.

How severe is CVE-2021-29521?

Low severity. CVSS v3 base score is 2.5 out of 10.

Vulnerability in Google Tensorflow

CVE-2021-29521

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<T>` (i.e., `std::vector<absl::flat_hash_map<int64,T>>`(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.

Published 2021-05-14 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 2.5 (Low). Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L.

EPSS exploit prediction

EPSS: 0.002 (7.6th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 8th percentile — 7.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

Google Tensorflow
Tensorflow — versions < 2.3.3, >= 2.4.0, < 2.4.2

Weakness classification (CWE)

CWE-131 — Incorrect Calculation of Buffer Size

References

github.com/tensorflow/tensorflow/security/advisories/GHSA-hr84-fqvp-48mm (Exploit, Patch, Third Party Advisory)
github.com/tensorflow/tensorflow/commit/c57c0b9f3a4f8684f3489dd9a9ec627ad8b599f5 (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-29521?: CVE-2021-29521 is a low-severity vulnerability in Google Tensorflow, classified under Incorrect Calculation of Buffer Size. CVSS score: 2.5/10. Published 2021-05-14.
How severe is CVE-2021-29521?: Low severity. CVSS v3 base score is 2.5 out of 10.