DEBIAN-CVE-2026-81722
nltk PorterStemmer in versions <= 3.10.2 (fixed in 3.10.3) contains an inefficient-algorithmic-complexity denial of service in PorterStemmer.stem(). The _is_consonant() helper walks backward over the entire run of trailing 'y' characters on every call, and _measure() invokes it for each stem position, causing O(n^2) behavior. A single ~20-50 KB untrusted token consisting of a long run of the letter 'y' followed by a matching suffix (e.g., 'ness') can pin a CPU core for seconds to minutes, causing availability impact.
DEBIAN-CVE-2026-81722
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:DEBIAN-CVE-2026-81722
nltk
Source reference: /affected/0/package/name
- Affected versions
- 3.10.0-1
Source reference:
/affected/0/versions3.10.1-1Source reference:
/affected/0/versions3.10.3-1Source reference:
/affected/0/versions3.8-1Source reference:
/affected/0/versions3.8.1-1Source reference:
/affected/0/versions3.9.1-1Source reference:
/affected/0/versions3.9.1-2Source reference:
/affected/0/versions3.9.2-1Source reference:
/affected/0/versions3.9.3-1Source reference:
/affected/0/versions - Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
nltk
Source reference: /affected/1/package/name
- Affected versions
- 3.10.0-1
Source reference:
/affected/1/versions3.10.1-1Source reference:
/affected/1/versions3.10.3-1Source reference:
/affected/1/versions3.9.1-2Source reference:
/affected/1/versions3.9.2-1Source reference:
/affected/1/versions3.9.3-1Source reference:
/affected/1/versions - Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
nltk
Source reference: /affected/2/package/name
- Affected versions
- 3.10.0-1
Source reference:
/affected/2/versions3.10.1-1Source reference:
/affected/2/versions3.9.1-2Source reference:
/affected/2/versions3.9.2-1Source reference:
/affected/2/versions3.9.3-1Source reference:
/affected/2/versions - Fixed versions
- 3.10.3-1
Source reference:
/affected/2/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "nltk",
"purl": "pkg:deb/debian/nltk?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
"3.10.0-1",
"3.10.1-1",
"3.10.3-1",
"3.8-1",
"3.8.1-1",
"3.9.1-1",
"3.9.1-2",
"3.9.2-1",
"3.9.3-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-81722.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "nltk",
"purl": "pkg:deb/debian/nltk?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"3.10.0-1",
"3.10.1-1",
"3.10.3-1",
"3.9.1-2",
"3.9.2-1",
"3.9.3-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-81722.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "3.10.3-1"
}
]
}
],
"package": {
"name": "nltk",
"purl": "pkg:deb/debian/nltk?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"3.10.0-1",
"3.10.1-1",
"3.9.1-2",
"3.9.2-1",
"3.9.3-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-81722.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
]Publisher severity
No explicit severity was provided.
- Event
- #58482 · Revision 1
- Added to Heist Feed
- Publisher date