Apache HTTP Server mod_http2 worker-thread starvation DoS
Apache HTTP Server 2.4.17 and 2.4.18 are vulnerable to a denial-of-service condition in HTTP/2 processing when mod_http2 is enabled. The flaw is caused by the server not limiting the number of simultaneous stream workers that can be consumed by a single HTTP/2 connection. A remote attacker can manipulate HTTP/2 flow-control windows so that stream-processing resources remain occupied, leading to worker-thread starvation for that connection and degrading or preventing normal request handling. The issue is described as a Slowloris-style HTTP/2 exhaustion problem tied to manipulated flow-control windows.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An HTTP/2 Slowloris-style denial-of-service issue tied to continuation frames and manipulated flow-control windows.
A Slowloris-style denial-of-service issue involving keeping legitimate connections open as long as possible to exhaust server resources.
A denial-of-service vulnerability involving worker-thread starvation in Apache HTTP Server over an HTTP/2 connection.
A prior related vulnerability referenced in connection with HTTP/2/HPACK denial-of-service issues.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.