PatchTheCVECVE-2026-81724: NLTK before 3.10.3 contains an uncontrolled recursion vulnerability in nltk.featstruct.FeatStructReader that a
CVE-2026-81724 is a medium-severity flaw (CVSS 5.3) affecting nltk. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
NLTK before 3.10.3 contains an uncontrolled recursion vulnerability in nltk.featstruct.FeatStructReader that allows unauthenticated attackers to cause a denial of service by supplying deeply nested feature-structure input. Attackers can craft trivial payloads with nested brackets that exceed Python's recursion limit and raise an unhandled RecursionError, crashing applications that parse user-supplied feature structures or feature grammars.
Why this priority
- Public exploit reference
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 5.3 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.5% (top 61%) |
| CISA exploited list | No |
| Weakness | CWE-674 |
| Published | 2026-08-27 |
| Last modified | 2026-08-31 |
Last updated 2026-08-31 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-81724?
nltk: upgrade to 3.10.3. Exact commands for each OS are on this page.
Is CVE-2026-81724 being exploited?
CVE-2026-81724 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-81724 affect?
CVE-2026-81724 affects nltk. Severity is medium (CVSS 5.3). NLTK before 3.10.3 contains an uncontrolled recursion vulnerability in nltk.featstruct.FeatStructReader that allows unauthenticated attackers to cause a denial of service by supplying deeply nested feature-structure input. Attackers can cra
How urgent is CVE-2026-81724?
Priority 38/100. Public exploit reference; Remotely exploitable, no login, no user action
Software pages
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