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No exploitation reportedFix available

CVE-2026-27651

No exploitation reported by the sources we read.

  • Published2026-03-24
  • Fixed inr35
  • WeaknessCWE-476

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

When the ngx_mail_auth_http_module module is enabled on NGINX Plus or NGINX Open Source, undisclosed requests can cause worker processes to terminate. This issue may occur when (1) CRAM-MD5 or APOP authentication is enabled, and (2) the authentication server permits retry by returning the Auth-Wait response header. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Timeline

dates in UTC
  1. 2026-03-2415:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-27651?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-27651?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
F5 nginx plus
BranchAffectedFixed in
—≥ r33, < r35r35
—= r32no fix published
—= r35no fix published
—= r36no fix published
F5 nginx open source
BranchAffectedFixed in
1.29≥ 1.29.0, < 1.29.71.29.7
1.x≥ 1.0.0, < 1.28.31.28.3
0.x≥ 0.5.15, ≤ 0.9.7no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

  • RHSA-2026:10065 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: Red Hat Update Infrastructure 5.1 security update

Full record on NVD

Fix

  1. Update F5 nginx plus to r35
  2. Vendor fix Red Hat Product Security RHSA-2026:10065 · 2 productsThe container images provided by this release, apart from the installer, should be deployed using rhui-installer utility. See the official documentation for more details.
  3. Workaround from the vendor Red Hat Product Security RHSA-2026:10065 · 4 productsMitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • NVDCVE recordread 2026-10-23
  • CISA-ADPSSVC decisionnone2026-03-24
  • OpenCVESSVC decisionnone—
  • CNACVSS 4.08.7read 2026-10-23
  • CNACVSS 3.17.5read 2026-10-23
  • CNAweakness (CWE)CWE-476read 2026-10-23
  • FIRST EPSSEPSS score1.7 %2026-10-22

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 4.0 vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/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
Published
2026-03-24
Last Modified
2026-07-15
NVD status
Modified

Frequently asked questions

What is CVE-2026-27651?

When the ngx_mail_auth_http_module module is enabled on NGINX Plus or NGINX Open Source, undisclosed requests can cause worker processes to terminate. This issue may occur when (1) CRAM-MD5 or APOP authentication is enabled, and (2) the authentication server permits retry by returning the Auth-Wait response header. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Is CVE-2026-27651 actively exploited?

Active exploitation of CVE-2026-27651 has not been confirmed. Its EPSS score was 1.7% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-27651?

CVE-2026-27651 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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