CVE-2026-28755 | NGINX ngx_stream_ssl_module vulnerability

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_stream_ssl_module module due to the improper handling of revoked certificates when configured with the ssl_verify_client on and ssl_ocsp on directives, allowing the TLS handshake to succeed even after an OCSP check identifies the certificate as revoked.   Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Published: 2026-03-24 Last update: 2026-03-26 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-28755 is rated Low Risk (21.5/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.01%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-28755

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-03-25 — 0.01% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-28755

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.3 4.0 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/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 Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network.
Attack complexity (AC:L)
Exploitation conditions are straightforward and stable.
Attack requirements (AT:N)
No additional preconditions are required beyond normal reachability.
Privileges required (PR:L)
Low privileges are required.
User interaction (UI:N)
No user interaction is required.
Vulnerable system confidentiality impact (VC:L)
Limited confidentiality impact on the vulnerable system.
Vulnerable system integrity impact (VI:L)
Limited integrity impact on the vulnerable system.
Vulnerable system availability impact (VA:N)
No availability impact on the vulnerable system.
Subsequent system confidentiality impact (SC:N)
No confidentiality impact on subsequent systems.
Subsequent system integrity impact (SI:N)
No integrity impact on subsequent systems.
Subsequent system availability impact (SA:N)
No availability impact on subsequent systems.
Exploit maturity (threat) (E:X)
Not defined: no reliable threat intelligence; scoring assumes the worst case (equivalent to Attacked).
Confidentiality requirement (CR:X)
Not defined: insufficient information; scoring treats this like High (worst case).
Integrity requirement (IR:X)
Not defined: insufficient information; scoring treats this like High (worst case).
Availability requirement (AR:X)
Not defined: insufficient information; scoring treats this like High (worst case).
Modified attack vector (MAV:X)
Not defined: scoring uses the Base Attack Vector (AV).
Modified attack complexity (MAC:X)
Not defined: scoring uses the Base Attack Complexity (AC).
Modified attack requirements (MAT:X)
Not defined: scoring uses the Base Attack Requirements (AT).
Modified privileges required (MPR:X)
Not defined: scoring uses the Base Privileges Required (PR).
Modified user interaction (MUI:X)
Not defined: scoring uses the Base User Interaction (UI).
Modified vulnerable system confidentiality impact (MVC:X)
Not defined: scoring uses the Base VC metric.
Modified vulnerable system integrity impact (MVI:X)
Not defined: scoring uses the Base VI metric.
Modified vulnerable system availability impact (MVA:X)
Not defined: scoring uses the Base VA metric.
Modified subsequent system confidentiality impact (MSC:X)
Not defined: scoring uses the Base SC metric.
Modified subsequent system integrity impact (MSI:X)
Not defined: scoring uses the Base SI metric.
Modified subsequent system availability impact (MSA:X)
Not defined: scoring uses the Base SA metric.
Safety (supplemental) (S:X)
Not evaluated.
Automatable (supplemental) (AU:X)
Not evaluated.
Recovery (supplemental) (R:X)
Not evaluated.
Value density (supplemental) (V:X)
Not evaluated.
Vulnerability response effort (supplemental) (RE:X)
Not evaluated.
Provider urgency (supplemental) (U:X)
Not evaluated.
 — — [email protected]
5.4 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.5 [email protected]
5.4 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.5 [email protected]

Weakness enumeration for CVE-2026-28755

OS Trackers for CVE-2026-28755

vendor priority summary link
alpine — CVE-2026-28755: 1 source package rows (nginx); 3 state rows across 3 repos (3.22-main, 3.23-main, edge-main); fixed 3, open 0. https://security.alpinelinux.org/vuln/CVE-2026-28755
debian unimportant CVE-2026-28755 unimportant priority: Debian including 1 source packages (nginx), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2026-28755
redhat medium — https://access.redhat.com/security/cve/CVE-2026-28755
suse medium CVE-2026-28755 severity moderate: SUSE including 4 source package names (nginx, nginx-1.29.7-1.1, nginx-source, nginx-source-1.29.7-1.1), 29 product×package rows across 15 product lines (SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS, SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS, … (15 product lines)): Known Not Affected 27, Fixed 2. https://www.suse.com/security/cve/CVE-2026-28755/
ubuntu medium CVE-2026-28755 medium priority: Ubuntu including 1 source packages (nginx), 9 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): not-affected 6, released 3. https://ubuntu.com/security/CVE-2026-28755

Affected software / configurations for CVE-2026-28755

Vendor Product Version Raw CPE
f5 nginx_plus r33 cpe:2.3:a:f5:nginx_plus:r33:*:*:*:*:*:*:*
f5 nginx_plus r33 cpe:2.3:a:f5:nginx_plus:r33:p1:*:*:*:*:*:*
f5 nginx_plus r33 cpe:2.3:a:f5:nginx_plus:r33:p2:*:*:*:*:*:*
f5 nginx_plus r33 cpe:2.3:a:f5:nginx_plus:r33:p3:*:*:*:*:*:*
f5 nginx_plus r34 cpe:2.3:a:f5:nginx_plus:r34:*:*:*:*:*:*:*
f5 nginx_plus r34 cpe:2.3:a:f5:nginx_plus:r34:p1:*:*:*:*:*:*
f5 nginx_plus r34 cpe:2.3:a:f5:nginx_plus:r34:p2:*:*:*:*:*:*
f5 nginx_plus r35 cpe:2.3:a:f5:nginx_plus:r35:p1:*:*:*:*:*:*
f5 nginx_plus r36 cpe:2.3:a:f5:nginx_plus:r36:*:*:*:*:*:*:*
f5 nginx_plus r36 cpe:2.3:a:f5:nginx_plus:r36:p1:*:*:*:*:*:*
f5 nginx_plus r36 cpe:2.3:a:f5:nginx_plus:r36:p2:*:*:*:*:*:*
f5 nginx_open_source >= 0.5.13, <= 0.9.7 cpe:2.3:a:f5:nginx_open_source:*:*:*:*:*:*:*:*
f5 nginx_open_source >= 1.27.2, < 1.28.3 cpe:2.3:a:f5:nginx_open_source:*:*:*:*:*:*:*:*
f5 nginx_open_source >= 1.29.0, < 1.29.7 cpe:2.3:a:f5:nginx_open_source:*:*:*:*:*:*:*:*

References for CVE-2026-28755

URL Tags
https://my.f5.com/manage/s/article/K000160368 Vendor Advisory Mitigation
cvelogic Threat Intelligence