CVE-2026-126297 json
NLTK before 3.10.4 CPU Denial of Service via ConllCorpusReader srl_instances
published 20d ago modified yesterday also EUVD-2026-125224 , GHSA-v8f3-6phw-6mh9
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.6%
- EPSS 0.6% chance of exploitation in 30 days, percentile 48%
- public exploits
- 0
- none known
Summary
NLTK before 3.10.4 contains a quadratic-time denial of service vulnerability in ConllCorpusReader._get_srl_instances that allows remote attackers to exhaust CPU through nested span rescans. Attackers can supply a crafted CoNLL SRL corpus with many predicates and span columns, placing the head span last, to pin a core for minutes.
Patch / fix
- pypi nltk 3.10.4
- nltk nltk 3.10.4
- github.com/nltk/nltk@7bae75f commit
- github.com/nltk/nltk@9cacbb9 commit
- github.com/nltk/nltk#3933 pull request
- github.com/nltk/nltk/releases/tag/v3.10.4 release
Is CVE-2026-126297 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
0.58% chance of exploitation in the next 30 days, higher than 48% of all scored CVEs (FIRST EPSS, 2026-11-14).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 8.7 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N |
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| GitHub | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| CNA | 4.0 | 8.7 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | nltk | <3.10.4 |
3.10.4 |
Affected products
- nltk nltk
Classification
References
-
github.com
/nltk/nltk/pull/3933
web
-
github.com
/nltk/nltk/commit/7bae75fc0f7b1f057ff7d89d24c81bb5a4a0f05a
web
-
github.com
/nltk/nltk/commit/9cacbb95d97eaac7debb30d6e7decbe74d2c635f
web
-
github.com
/nltk/nltk/security/advisories/GHSA-v8f3-6phw-6mh9
vendor-advisory, web, advisory
-
vulncheck.com
/advisories/nltk-before-3.10.4-cpu-denial-of-service-via-conllcorpusreader-srl-instances
third-party-advisory, web
-
nvd.nist.gov
/vuln/detail/CVE-2026-126297
advisory
-
github.com
/nltk/nltk
package
-
github.com
/nltk/nltk/releases/tag/v3.10.4
web
Sources
- CVE List CVE-2026-126297
- GitHub Advisory GHSA-v8f3-6phw-6mh9
- NVD CVE-2026-126297
- Maintainer advisory GHSA-v8f3-6phw-6mh9
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.