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CVE-2026-62911

HIGH 8

Published 2026-08-11 · Last modified 2026-08-21

Authentication bypass by capture-replay in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.

ELEVATED IMPACT

Severe if exploited (CVSS 8), but no known exploitation and low modeled probability. Patch on a normal cadence.

Exploitation likelihood

0.7%chance of exploitation in 30 days · 51st percentile

○ In CISA KEV ○ Public exploit / PoC

Impact if exploited

8CVSS 3.1 · HIGH

  • ConfidentialityHigh
  • IntegrityHigh
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ⚠Privileges: Requires a low-privilege account
  • ⚠User interaction: A user must take an action (click / open a file)
  • ✓Complexity: No special conditions — reliably repeatable

✓ 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-2026-62911/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-2026-62911/poc.json

Affected

Vendors Microsoft

Products Microsoft Exchange Server 2016 Cumulative Update 23 Microsoft Exchange Server 2019 Cumulative Update 14 Microsoft Exchange Server 2019 Cumulative Update 15 Microsoft Exchange Server Subscription Edition Rtm Exchange Server Exchange Server Subscription Edition

Weakness (CWE)

  • CWE-294: : Authentication Bypass by Capture-replay

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

Known Affected Software Configurations

VendorProductVersion range
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2016
MicrosoftExchange Server2019
MicrosoftExchange Server2019
MicrosoftExchange Server2019
MicrosoftExchange Server2019
MicrosoftExchange Server2019
MicrosoftExchange Server2019
MicrosoftExchange Server2019
MicrosoftExchange Server2019
MicrosoftExchange Server2019
MicrosoftExchange Server2019
MicrosoftExchange Server2019
MicrosoftExchange Server2019
MicrosoftExchange Server2019
MicrosoftExchange Server2019
MicrosoftExchange Server Subscription Edition< 15.02.2562.046

All CVSS metrics

  • HIGH 8 v3.1 · CNA Primary
    CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
  • HIGH 8 v3.1 · NVD Secondary
    CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

References

Patches & mitigations

Sources: NVD · CVE.org · EPSS