GHSA-98qm-wvgf-w4cf

Suggest an improvement
Source
https://github.com/advisories/GHSA-98qm-wvgf-w4cf
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-98qm-wvgf-w4cf/GHSA-98qm-wvgf-w4cf.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-98qm-wvgf-w4cf
Aliases
Published
2026-10-27T15:36:35Z
Modified
2026-10-27T15:47:24Z
Severity
  • 8.2 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N CVSS Calculator
Summary
MongoDB Python Driver: Out-of-bounds read in BSON decoding via a malformed Regex element
Details

Impact

The C extension's BSON decoder scans a Regex element's pattern and flags strings with strlen before checking the document's remaining length, so a crafted truncated Regex element can read past the end of the caller's buffer. bson.decode and bson.decode_all accept mmap and array buffers, which carry no NUL sentinel; the read can cross into unmapped memory and kill the process with an uncatchable SIGSEGV. Any application decoding untrusted BSON from such buffers is affected — impact is availability only, since the out-of-bounds bytes are never returned as content. NUL-terminated buffers (bytes, bytearray) raise InvalidBSON at worst; the driver's own transport and pure-Python installs are not affected. All releases through 4.18.2 are affected when the C extension is loaded.

Patches

Fixed in PyMongo 4.18.3. Malformed Regex elements now raise InvalidBSON on every accepted buffer type; valid documents decode unchanged.

Workarounds

Decode untrusted BSON only from NUL-terminated buffers — bytes or bytearray — and copy mmap input first, e.g. bytes(mm[:size]).

Database specific 
{
    "cwe_ids":  [
        "CWE-125"
    ],
    "github_reviewed":  true,
    "github_reviewed_at":  "2026-10-27T15:36:35Z",
    "nvd_published_at":  null,
    "severity":  "HIGH"
}
References

Affected packages

PyPI / pymongo

Package

Name
pymongo
View open source insights on deps.dev
Purl
pkg:pypi/pymongo

Affected ranges

Type
ECOSYSTEM
Events
Introduced
3.9.0
Fixed
4.18.3

Affected versions

3.*
3.9.0
3.10.0
3.10.1
3.11.0
3.11.1
3.11.2
3.11.3
3.11.4
3.12.0
3.12.1
3.12.2
3.12.3
3.13.0
4.*
4.0
4.0.1
4.0.2
4.1.0
4.1.1
4.2.0
4.3.2
4.3.3
4.4.0b0
4.4.0
4.4.1
4.5.0
4.6.0
4.6.1
4.6.2
4.6.3
4.7.0
4.7.1
4.7.2
4.7.3
4.8.0b0
4.8.0
4.9
4.9.1
4.9.2
4.10.0
4.10.1
4.11
4.11.1
4.11.2
4.11.3
4.12.0
4.12.1
4.13.0.dev0
4.13.0
4.13.1
4.13.2
4.14.0
4.14.1
4.15.0
4.15.1
4.15.2
4.15.3
4.15.4
4.15.5
4.16.0.dev0
4.16.0
4.17.0
4.18.0
4.18.1
4.18.2

Database specific

last_known_affected_version_range 
"<= 4.18.2"
source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-98qm-wvgf-w4cf/GHSA-98qm-wvgf-w4cf.json"