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HTTP/2 Servers CVE-2026-44909

CRITICAL
2026-07-16
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Severity by source

vuln.today AI
7.5 HIGH

Network-accessible unauthenticated attack using standard protocol frames with no interaction required; sole impact is availability with no confidentiality or integrity loss.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Lifecycle Timeline

2
Analysis Generated
Jul 16, 2026 - 20:23 vuln.today
CVE Published
Jul 16, 2026 - 19:27 oss-security
CRITICAL

Description PRE-NVD

Disclosed via oss-security. NVD scoring and full description are pending.

AnalysisAI

Memory exhaustion and denial-of-service across HTTP/2 server implementations allow remote unauthenticated attackers to crash or severely degrade affected services by intentionally stalling flow control using standard HTTP/2 protocol frames. Researched and reported by the Okta Red Team and coordinated through CERT/CC as VU#885548, this class of vulnerability is tracked across three CVEs (CVE-2026-59762, CVE-2026-59173, CVE-2026-44909) affecting multiple vendor implementations including F5 BIG-IP. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Recon
Establish many HTTP/2 connections to target
Delivery
Open maximum concurrent streams per connection
Exploit
Request large server-side resources
Install
Send SETTINGS_INITIAL_WINDOW_SIZE=0, withhold WINDOW_UPDATE frames
C2
Server buffers full response data, unable to transmit
Execute
Memory and worker resources exhausted
Impact
Service unavailable to legitimate users

Vulnerability AssessmentAI

Exploitation The target server must be running an HTTP/2 implementation that does not enforce memory ceilings on buffered response data and does not terminate connections that remain flow-control-stalled beyond a configurable duration - this is the specific vulnerable configuration. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment Real-world risk is high for any organization exposing HTTP/2-capable servers directly to the internet. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker opens many simultaneous HTTP/2 connections to a publicly accessible web server, on each connection opening the protocol-maximum number of concurrent streams and issuing requests for large resources such as file downloads or bulk API responses. Immediately after sending requests, the attacker transmits a SETTINGS frame advertising SETTINGS_INITIAL_WINDOW_SIZE=0 and ceases sending any WINDOW_UPDATE frames, legally freezing the server's ability to transmit response data on all active streams. …
Remediation Several vendors have released patches addressing implementations covered by the VU#885548 disclosure; consult CERT/CC VU#885548 at https://kb.cert.org/vuls/id/885548 for the full vendor matrix and individual fix references. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, conduct a complete inventory of F5 BIG-IP and all HTTP/2-enabled servers in your environment, identify internet-facing deployments, and enable HTTP/2 protocol logging. …

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CVE-2026-44909 vulnerability details – vuln.today

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