Description
NLTK before 3.10.3 contains a regular expression denial of service vulnerability in Pl196xCorpusReader that allows attackers to cause quadratic CPU consumption by supplying malformed TEI blocks with many unmatched opening tags. Attackers can exploit lazy regex patterns in the read_block method through public APIs like words() and tagged_words() to force repeated rescans and achieve near-quadratic runtime growth.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| nltk | nltk | < 3.10.3 | 3.10.3 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | nltk | 3.10.3-1 | — |
| Debian 13 | nltk | No fix yet | — |
| Debian 12 | nltk | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 26.04 LTS | nltk | No fix yet | — |
| Ubuntu Pro 24.04 LTS | nltk | No fix yet | — |
| Ubuntu Pro 22.04 LTS | nltk | No fix yet | — |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | nltk | No fix yet | — |
| Ubuntu Pro 18.04 LTS | nltk | No fix yet | — |
| Ubuntu Pro 16.04 LTS | nltk | No fix yet | — |
| Ubuntu Pro 14.04 LTS | nltk | No fix yet | — |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| PyPI | nltk | < 3.10.3 | 3.10.3 | GHSA-8mpw-7fpc-4gqj |
References
- GitHub Security Advisory (GHSA-8mpw-7fpc-4gqj) vendor-advisory
- VulnCheck Advisory: NLTK before 3.10.3 Regular Expression Denial of Service via Pl196xCorpusReader third-party-advisory