CVE-2026-123378
A NVD · · CVE-2026-123378
Admiralty grading (A–F · 1–6)
Source reliability
- A Completely reliable
- B Usually reliable
- C Fairly reliable
- D Not usually reliable
- E Unreliable
- F Cannot be judged
Information credibility
- 1 Confirmed
- 2 Probably true
- 3 Possibly true
- 4 Doubtful
- 5 Improbable
- 6 Cannot be judged
NATO Admiralty (AJP-2.1) grades confidence, independent of the risk score. Cross-source corroboration isn't tracked for non-CVE news, so single-source items are capped at a lower credibility number; a low number does not imply low quality.
Key metrics
- CVSS
- 7.5
- EPSS
- 0%
Key insight
The NVD entry provides no information beyond the CVE description regarding exploitation or attackers.
Description
CVE-2026-123378 affects Microsoft Office Outlook and is based on an integer overflow or wraparound. An unauthorized attacker can thereby execute code over the network. The entry comes from NVD and contains no information on active exploitation, proof of concept, or CISA KEV inclusion. Systems with vulnerable Outlook versions are affected; details on affected builds or CVSS are not available from the short description.
Risk score
- cvss base
- 75.00
- kev bonus
- 0.00
- epss bonus
- 0.00
- poc bonus
- 0.00
- raw before weight
- 75.00
- industry weight
- 1.21
- freshness factor
- 1.00
- exploitability factor
- 1.00
- days old
- 0.00
- vendor mismatch penalty
- 0.00
Path: operational
MITRE ATT&CK mapping
1 TTPProcedure details
| Technique | Tactic | Procedure | Conf. | Source |
|---|---|---|---|---|
| T1203 Exploitation for Client Execution | Execution | An attacker exploits an integer overflow vulnerability in Microsoft Office Outlook by sending maliciously crafted data over the network to the Outlook client, causing code execution. | high | llm |