CVE-2026-80205High· 7.5▾ TwilightA flaw was found in NLTK. A remote attacker can exploit a regular expression denial of service (ReDoS) vulnerability in the `Text.findall()` and `TokenSearcher.findall()` methods. These methods accept user-supplied regular expressions with…
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 41.3 · likelihood 0.1 · exploitation 0
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Exploit-prediction probability, daily snapshots since Sep 2.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via CSAF
0.5%
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Last analysed / modified upstream
A flaw was found in NLTK. A remote attacker can exploit a regular expression denial of service (ReDoS) vulnerability in the Text.findall() and TokenSearcher.findall() methods. These methods accept user-supplied regular expressions without validation, allowing an attacker to provide crafted patterns that cause catastrophic backtracking. This can lead to indefinite CPU saturation, resulting in a denial of service to all users of the Python process.
nltk: NLTK: Denial of Service via unvalidated regular expressions — rated Important by Red Hat. Released 2026-08-26, updated 2026-10-19.
Affected:
Fixed:
No fix planned:
Not affected:
For Red Hat OpenShift AI 3.3.7 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update:
https://docs.redhat.com/en/documentation/red_hat_openshift_ai/ https://access.redhat.com/errata/RHSA-2026:73987 For Red Hat OpenShift AI 3.4.5 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update:
https://docs.redhat.com/en/documentation/red_hat_openshift_ai/ https://access.redhat.com/errata/RHSA-2026:84734 For Red Hat OpenShift AI 3.5.1 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update:
https://docs.redhat.com/en/documentation/red_hat_openshift_ai/ https://access.redhat.com/errata/RHSA-2026:69539
Workarounds / mitigations:
Text.findall() or TokenSearcher.findall() to prevent execution of arbitrary or unvalidated regular expressions, or enforce execution timeouts via worker process isolation to bound CPU consumption.Affected packages:
nltk < 3.10.0Patched in:
nltk 3.10.0Field changes observed since this record was first indexed.
Connected by shared product, vendor, weakness, or advisory.
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