Python/nltk/3.5
Natural Language Toolkit
https://pypi.org/project/nltk
Apache-2.0
4 Security Vulnerabilities
NLTK Vulnerable to REDoS
- https://nvd.nist.gov/vuln/detail/CVE-2021-3828
- https://github.com/advisories/GHSA-2ww3-fxvq-293j
- https://github.com/nltk/nltk/pull/2816
- https://github.com/nltk/nltk/commit/277711ab1dec729e626b27aab6fa35ea5efbd7e6
- https://huntr.dev/bounties/d19aed43-75bc-4a03-91a0-4d0bb516bc32
- https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2021-356.yaml
The nltk package is vulnerable to ReDoS (regular expression denial of service). An attacker that is able to provide as an input to the [_read_comparison_block()
(https://github.com/nltk/nltk/blob/23f4b1c4b4006b0cb3ec278e801029557cec4e82/nltk/corpus/reader/comparative_sents.py#L259) function in the file nltk/corpus/reader/comparative_sents.py
may cause an application to consume an excessive amount of CPU.
ntlk unsafe deserialization vulnerability
- https://nvd.nist.gov/vuln/detail/CVE-2024-39705
- https://github.com/nltk/nltk/issues/2522
- https://github.com/nltk/nltk/issues/3266
- https://github.com/advisories/GHSA-cgvx-9447-vcch
- https://github.com/nltk/nltk/commit/441aecb7d33014bd08672232c6c8bb69c2ceaba2
- https://www.vicarius.io/vsociety/posts/rce-in-python-nltk-cve-2024-39705-39706
NLTK through 3.8.1 allows remote code execution if untrusted packages have pickled Python code, and the integrated data package download functionality is used. This affects, for example, averagedperceptrontagger and punkt.
Inefficient Regular Expression Complexity in nltk (word_tokenize, sent_tokenize)
- https://github.com/nltk/nltk/security/advisories/GHSA-f8m6-h2c7-8h9x
- https://nvd.nist.gov/vuln/detail/CVE-2021-43854
- https://github.com/nltk/nltk/issues/2866
- https://github.com/nltk/nltk/pull/2869
- https://github.com/nltk/nltk/commit/1405aad979c6b8080dbbc8e0858f89b2e3690341
- https://github.com/advisories/GHSA-f8m6-h2c7-8h9x
- https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2021-859.yaml
Impact
The vulnerability is present in PunktSentenceTokenizer
, sent_tokenize
and word_tokenize
. Any users of this class, or these two functions, are vulnerable to a Regular Expression Denial of Service (ReDoS) attack.
In short, a specifically crafted long input to any of these vulnerable functions will cause them to take a significant amount of execution time. The effect of this vulnerability is noticeable with the following example:
```python
from nltk.tokenize import word_tokenize
n = 8
for length in [10**i for i in range(2, n)]:
# Prepare a malicious input
text = a
* length
startt = time.time()
# Call `wordtokenizeand naively measure the execution time
word_tokenize(text)
print(f"A length of {length:<{n}} takes {time.time() - start_t:.4f}s")
Which gave the following output during testing:
python
A length of 100 takes 0.0060s
A length of 1000 takes 0.0060s
A length of 10000 takes 0.6320s
A length of 100000 takes 56.3322s
...
``
I canceled the execution of the program after running it for several hours.
If your program relies on any of the vulnerable functions for tokenizing unpredictable user input, then we would strongly recommend upgrading to a version of NLTK without the vulnerability, or applying the workaround described below.
Patches
The problem has been patched in NLTK 3.6.6. After the fix, running the above program gives the following result:
python
A length of 100 takes 0.0070s
A length of 1000 takes 0.0010s
A length of 10000 takes 0.0060s
A length of 100000 takes 0.0400s
A length of 1000000 takes 0.3520s
A length of 10000000 takes 3.4641s
This output shows a linear relationship in execution time versus input length, which is desirable for regular expressions.
We recommend updating to NLTK 3.6.6+ if possible.
Workarounds
The execution time of the vulnerable functions is exponential to the length of a malicious input. With other words, the execution time can be bounded by limiting the maximum length of an input to any of the vulnerable functions. Our recommendation is to implement such a limit.
References
- The issue showcasing the vulnerability: https://github.com/nltk/nltk/issues/2866
- The pull request containing considerably more information on the vulnerability, and the fix: https://github.com/nltk/nltk/pull/2869
- The commit containing the fix: 1405aad979c6b8080dbbc8e0858f89b2e3690341
- Information on CWE-1333: Inefficient Regular Expression Complexity: https://cwe.mitre.org/data/definitions/1333.html
For more information
If you have any questions or comments about this advisory: * Open an issue in github.com/nltk/nltk * Email us at nltk.team@gmail.com
NLTK Vulnerable to REDoS
- https://nvd.nist.gov/vuln/detail/CVE-2021-3842
- https://github.com/nltk/nltk/commit/2a50a3edc9d35f57ae42a921c621edc160877f4d
- https://huntr.dev/bounties/761a761e-2be2-430a-8d92-6f74ffe9866a
- https://github.com/advisories/GHSA-rqjh-jp2r-59cj
- https://github.com/nltk/nltk/pull/2906
- https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2022-5.yaml
NLTK is vulnerable to REDoS in some RegexpTaggers used in the functions get_pos_tagger
and malt_regex_tagger
.
63 Other Versions
Version | License | Security | Released | |
---|---|---|---|---|
3.9.1 | Apache-2.0 | |||
3.9 | Apache-2.0 | |||
3.8.2 | Apache-2.0 | 1 | ||
3.8.1 | Apache-2.0 | 1 | ||
3.8 | Apache-2.0 | 1 | ||
3.7 | Apache-2.0 | 1 | 2022-02-09 - 12:40 | over 2 years |
3.6.7 | Apache-2.0 | 1 | 2021-12-28 - 23:28 | almost 3 years |
3.6.6 | Apache-2.0 | 1 | 2021-12-21 - 02:16 | almost 3 years |
3.6.5 | Apache-2.0 | 3 | 2021-10-11 - 03:49 | about 3 years |
3.6.4 | Apache-2.0 | 3 | 2021-10-01 - 01:58 | about 3 years |
3.6.3 | Apache-2.0 | 4 | 2021-09-20 - 06:00 | about 3 years |
3.6.2 | Apache-2.0 | 4 | 2021-04-20 - 07:42 | over 3 years |
3.6.1 | Apache-2.0 | 4 | 2021-04-07 - 21:36 | over 3 years |
3.6 | Apache-2.0 | 4 | 2021-04-07 - 10:49 | over 3 years |
3.5 | Apache-2.0 | 4 | 2020-04-12 - 23:46 | over 4 years |
3.4.5 | Apache-2.0 | 4 | 2019-08-20 - 10:55 | about 5 years |
3.4.4 | Apache-2.0 | 5 | 2019-07-04 - 11:09 | over 5 years |
3.4.3 | Apache-2.0 | 5 | 2019-06-06 - 17:52 | over 5 years |
3.4.2 | Apache-2.0 | 5 | 2019-06-06 - 04:02 | over 5 years |
3.4.1 | Apache-2.0 | 5 | 2019-04-17 - 10:48 | over 5 years |
3.4 | Apache-2.0 | 5 | 2018-11-17 - 08:04 | almost 6 years |
3.3 | Apache-2.0 | 5 | 2018-05-06 - 02:27 | over 6 years |
3.2.5 | Apache-2.0 | 5 | 2017-09-24 - 11:36 | about 7 years |
3.2.4 | Apache-2.0 | 5 | 2017-05-20 - 22:49 | over 7 years |
3.2.3 | Apache-2.0 | 5 | 2017-05-17 - 20:59 | over 7 years |
3.2.2 | Apache-2.0 | 5 | 2016-12-31 - 21:47 | almost 8 years |
3.2.1 | Apache-2.0 | 5 | 2016-04-09 - 10:06 | over 8 years |
3.2 | Apache-2.0 | 5 | 2016-03-03 - 01:12 | over 8 years |
3.1 | Apache-2.0 | 5 | 2015-10-15 - 19:51 | about 9 years |
3.0.5 | Apache-2.0 | 5 | 2015-09-06 - 02:51 | about 9 years |
3.0.4 | Apache-2.0 | 5 | 2015-07-13 - 01:39 | over 9 years |
3.0.3 | Apache-2.0 | 5 | 2015-06-11 - 10:59 | over 9 years |
3.0.2 | Apache-2.0 | 5 | 2015-03-13 - 03:43 | over 9 years |
3.0.1 | Apache-2.0 | 5 | 2015-01-12 - 23:11 | almost 10 years |
3.0.0 | Apache-2.0 | 5 | 2015-01-12 - 00:24 | almost 10 years |
3.0.0b2 | Apache-2.0 | 5 | 2014-08-26 - 00:56 | about 10 years |
3.0.0b1 | Apache-2.0 | 5 | 2014-07-11 - 13:32 | over 10 years |
2.0.5 | Apache-2.0 | 5 | 2015-01-12 - 22:55 | almost 10 years |
2.0.4 | Apache-2.0 | 5 | 2015-01-12 - 22:58 | almost 10 years |
2.0.3 | Apache-2.0 | 5 | 2012-09-24 - 09:34 | about 12 years |
2.0.2 | Apache-2.0 | 5 | 2012-07-05 - 12:08 | over 12 years |
2.0.1 | Apache-2.0 | 5 | 2012-05-15 - 04:29 | over 12 years |
2.0.1rc4 | Apache-2.0 | 5 | 2012-02-10 - 00:01 | over 12 years |
2.0.1rc3 | Apache-2.0 | 5 | 2012-01-07 - 06:41 | almost 13 years |
2.0.1rc1 | Apache-2.0 | 5 | 2011-04-11 - 08:04 | over 13 years |
2.0.1rc2-git | Apache-2.0 | 5 | 2011-12-01 - 04:45 | almost 13 years |
0.9.9 | GPL | 5 | ||
0.9.8 | GPL | 5 | ||
0.9.7 | GPL | 5 | ||
0.9.6 | GPL | 5 | ||
0.9.5 | GPL | 5 | ||
0.9.4 | GPL | 5 | ||
0.9.3 | GPL | 5 | ||
0.9 | GPL | 5 | ||
0.8 | GPL | 5 | ||
2.0b7 | Apache-2.0 | 5 | 2009-11-09 - 14:20 | almost 15 years |
2.0b6 | Apache-2.0 | 5 | 2009-09-25 - 10:31 | about 15 years |
2.0b8 | Apache-2.0 | 5 | 2010-03-10 - 20:30 | over 14 years |
2.0b4 | Apache-2.0 | 5 | 2009-07-15 - 09:32 | over 15 years |
2.0b5 | Apache-2.0 | 5 | 2009-07-19 - 10:20 | over 15 years |
2.0b9 | Apache-2.0 | 5 | 2010-08-23 - 07:46 | about 14 years |
3.5b1 | Apache-2.0 | 4 | 2020-03-08 - 00:48 | over 4 years |
3.9b1 | Apache-2.0 | 1 |