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CVE-2026-106431

MEDIUM 5.9

Published 2026-10-08 · Last modified 2026-10-08

An off-by-one error in the BSON bulk document writer in the MongoDB C Driver can write one zero byte immediately past a heap allocation when a document ends at a specific buffer boundary. An actor who can influence the size of documents serialized by an embedding application can corrupt adjacent process memory or terminate the process. Reaching this issue requires the application to use the BSON bulk-writer API and produce a precise cumulative document size.

NO EXPLOITATION SIGNALS

No known exploitation, public exploit, or elevated probability at this time. Track for changes.

Exploitation likelihood

0.1%chance of exploitation in 30 days · 1st percentile

○ In CISA KEV ○ Public exploit / PoC

Impact if exploited

5.9CVSS 4.0 · MEDIUM

  • ConfidentialityNone
  • IntegrityLow
  • AvailabilityHigh

What an attacker needs

  • ⚠Access: Requires local access to the host
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable
  • ⚠Requirements: Specific conditions must be present

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept & exploit code

Test against your own equipment

curl -s https://vulnpedia.com/cve/CVE-2026-106431/poc.jsonMachine-readable PoC index for this CVE (for automation).

Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-106431/poc.json

Affected

Vendors Mongodb

Products C Driver

Weakness (CWE)

  • CWE-787: : Out-of-bounds Write

CVSS vector

CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N

All CVSS metrics

  • MEDIUM 5.9 v4.0 · CNA Primary
    CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
  • MEDIUM 5.7 v3.1 · CNA Primary
    CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
  • MEDIUM 5.9 v4.0 · NVD Secondary
    CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/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
  • MEDIUM 5.7 v3.1 · NVD Secondary
    CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H

References

Technical & other

Sources: NVD · CVE.org · EPSS