CVE-2026-126300 json
NLTK from 3.2.5 before 3.10.4 CPU Exhaustion via TreebankWordTokenizer.span_tokenize
published 20d ago modified yesterday also EUVD-2026-125221 , GHSA-ffr9-mgrr-wcvr
- cvss
- 5.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.5%
- EPSS 0.5% chance of exploitation in 30 days, percentile 41%
- public exploits
- 0
- none known
Summary
NLTK from 3.2.5 before 3.10.4 contains an algorithmic complexity vulnerability in TreebankWordTokenizer.span_tokenize that allows remote attackers to cause quadratic CPU consumption through repeated list.pop(0) calls. Attackers can submit long runs of double-quote characters to services span-tokenizing untrusted text, exhausting a CPU core and degrading availability.
Patch / fix
- pypi nltk 3.10.4
- nltk nltk 3.10.4
- github.com/nltk/nltk@e20c40e commit
- github.com/nltk/nltk#3895 pull request
- github.com/nltk/nltk/releases/tag/v3.10.4 release
Is CVE-2026-126300 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerExploit prediction
0.47% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-14).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 6.9 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N |
| CNA | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| GitHub | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| CNA | 4.0 | 6.9 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
| NVD | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | nltk | >=3.2.5, <3.10.4 |
3.10.4 |
Affected products
- nltk nltk
Classification
References
-
github.com
/nltk/nltk/pull/3895
web
-
github.com
/nltk/nltk/commit/e20c40e26ec9306de885703f6e53250695f1f49b
web
-
github.com
/nltk/nltk/security/advisories/GHSA-ffr9-mgrr-wcvr
vendor-advisory, web, advisory
-
vulncheck.com
/advisories/nltk-from-3.2.5-before-3.10.4-cpu-exhaustion-via-treebankwordtokenizer-span-tokenize
third-party-advisory, web
-
nvd.nist.gov
/vuln/detail/CVE-2026-126300
advisory
-
github.com
/nltk/nltk
package
-
github.com
/nltk/nltk/releases/tag/v3.10.4
web
Sources
- CVE List CVE-2026-126300
- GitHub Advisory GHSA-ffr9-mgrr-wcvr
- NVD CVE-2026-126300
- Maintainer advisory GHSA-ffr9-mgrr-wcvr
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
The maintainers of nltk/nltk published their own advisory on GitHub. Reviewed sources take precedence over it.