What is CVE-2026-96749?

CVE-2026-96749 is Heap out-of-bounds write via signed size overflow in BSON document encoding. The supplied enrichment data classifies it as Memory Corruption mapped to CWE-190 Integer Overflow or Wraparound.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Active exploitation is not confirmed from current sources for CVE-2026-96749. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-96749 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

A public PoC is not confirmed from current sources for CVE-2026-96749. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with Not reported where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-96749 using CVSS 8.4, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

highMemory Corruption

CVE-2026-96749

CVE-2026-96749 — Heap out-of-bounds write via signed size overflow in BSON document encoding

An integer overflow in the BSON document encoding component of the MongoDB Python Driver's bundled native extension may occur when a single document is built from an unusually large amount of caller-supplied data. Size arithmetic is performed in a signed 32-bit type, and the guard meant to catch the overflow is written in a form whose behavior is not defined by the C language standard. A party with no privileges who can place a very large value into data that an application encodes may, depending on how the native extension was built, cause a write outside the bounds of an allocated buffer inside the application's own process.

Published Sep 24, 2026Updated Sep 26, 2026Sources: NVD, MongoDB (CNA), GitHub, Red Hat (VEX)

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Unreported

no source claims exploitation

EPSS

chance of exploitation in 30 days

Affects

MongoDB

Python Driver

CVSS base

8.4

high · 2 sources

CISA SSVC assessment

Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.

CISA

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script all four kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

The vendor's own words where we have them.

Upgrade Python Driver to a fixed release. Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

Red Hat VEX · CVE-2026-96749

fixed0affected23not affected0

none_available: Affected

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
MongoDB	Python Driver	1.9.0 to < 4.18.2	Vulnerable

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Availability

High

Confidentiality

High

Integrity

High

Scope

Unchanged

Attack Complexity

Low

Attack Vector

Local

Privileges Req

None

User Interaction

None

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
8.4	CVSS 3.1	high	2.5	5.9	mongodb.com (CNA), MongoDB (CNA), Red Hat (VEX)
7.5	CVSS 4.0	high	—	—	MongoDB (CNA)

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Weakness & attack patterns

CWE-190Integer Overflow or Wraparound

Inferred from the weakness class — not observed against this CVE.

CAPEC-100 · Overflow BuffersCAPEC-123 · Buffer Manipulation

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · CVSS 3.1 8.4 (AV:L)
Sep 26, 2026 · NVD
Initial · CVE published
Sep 24, 2026 · NVD

References

7 on the record

github.com/mongodb/mongo-python-driver/blob/4.18.2/doc/changelog.rst
Exploit, Third Party Advisory
github.com/mongodb/mongo-python-driver/releases/tag/4.18.2
Exploit, Third Party Advisory
github.com/mongodb/mongo-python-driver/security/advisories/GHSA-v4x9-3549-crwv
Exploit, Third Party Advisory
access.redhat.com/security/cve/CVE-2026-96749
Vendor Advisory
bugzilla.redhat.com/show_bug.cgi?id=2540688
Vendor Advisory
www.cve.org/CVERecord?id=CVE-2026-96749
Vendor Advisory
nvd.nist.gov/vuln/detail/CVE-2026-96749
NVD

Elsewhere on this site

MongoDBevery CVE for this vendor
Memory Corruptionsame class
CWE-190other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-96749 is Heap out-of-bounds write via signed size overflow in BSON document encoding, a high vulnerability affecting Python Driver from MongoDB. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-96749. Public exploit evidence is: A public PoC is not confirmed from current sources for CVE-2026-96749. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 8.4 describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.