Apache HTTP Server deployments using affected mod_http2 builds must patch now. Exhausted file handles can trigger memory corruption in HTTP/2 request handling.
Impact
Apache has fixed CVE-2026-48913, a use-after-free vulnerability in the Apache HTTP Server mod_http2 module. The flaw affects Apache HTTP Server 2.4.55 through 2.4.67. The fix is Apache HTTP Server 2.4.68.
Patch affected servers now.
The issue occurs when file handles are already exhausted. That condition matters. File descriptor exhaustion is not rare on internet-facing servers. It can occur during traffic spikes, slow-client behavior, backend instability, logging failures, badly sized limits, or deliberate resource pressure. Once the server enters that stressed state, vulnerable mod_http2 code can mishandle memory lifetime and access freed memory.
NVD lists a CISA-ADP CVSS 3.1 score of 7.3, High, with vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L in the CVE-2026-48913 record. Apache rates the issue as low in its Apache HTTP Server 2.4 vulnerability advisory. Treat the operational risk as real where HTTP/2 is enabled and Apache is exposed to untrusted traffic.
Affected Products
Affected product: Apache HTTP Server.
Affected component: mod_http2.
Affected versions: Apache HTTP Server 2.4.55 through 2.4.67.
Fixed version: Apache HTTP Server 2.4.68, released June 8, 2026.
The vulnerable module provides HTTP/2 support for Apache httpd. Apache documents mod_http2 as the module that implements the HTTP/2 transport layer and relies on libnghttp2 for the core protocol engine. Operators enable it through the Protocols directive, commonly with h2 for HTTP/2 over TLS or h2c for cleartext HTTP/2. See the official mod_http2 documentation for deployment details.
Severity
CVE ID: CVE-2026-48913.
Weakness: CWE-416, use after free.
CVSS: 7.3 High, CISA-ADP assessment.
Apache impact rating: low.
Attack requirements: network access, low attack complexity, no privileges, no user interaction, according to the CVSS vector published by NVD.
The split between Apache impact and CVSS severity is significant. Apache’s impact rating reflects project-specific assessment. CVSS describes generic exploitability and impact characteristics. Security teams should not ignore the CVSS vector. The vulnerability is network reachable in affected configurations and does not require authentication.
Technical Details
This is a memory safety bug.
A use-after-free occurs when code continues to use memory after it has been released. The program may read stale data. It may write into memory that now belongs to another object. It may crash. In some bug classes, an attacker can shape memory reuse and influence behavior after the stale pointer is accessed.
The affected area is HTTP/2 handling in Apache httpd. HTTP/2 is more stateful than HTTP/1.1. One client connection can carry many streams. The server tracks stream state, flow control, output buffers, worker activity, and file-backed responses. Apache’s own documentation warns that enabling HTTP/2 changes resource consumption because mod_http2 uses worker threads and keeps more per-connection state than HTTP/1.1.
CVE-2026-48913 is tied to file handle exhaustion. That condition is important because file descriptors are a shared process resource. Apache needs them for sockets, logs, files, pipes, proxied connections, and modules. When the available handle pool is depleted, normal request paths begin to fail. Error handling paths then run more often. Bugs often hide there.
The vulnerable condition involves mod_http2 when file handles are already exhausted. Apache’s advisory describes the result as memory corruption. NVD describes it as a use-after-free. Together, that points to a lifetime error in a stressed resource path, not a routine parsing flaw.
HTTP/2 makes this risk sharper. A single connection can create many streams. Each stream can interact with response generation and buffering. If a server is already close to its file descriptor limit, multiplexed traffic can increase pressure. That does not mean HTTP/2 is unsafe by design. It means capacity limits, module versions, and patch levels matter.
What To Do
Upgrade Apache HTTP Server to 2.4.68 immediately. Apache lists 2.4.68 as the fixed release for CVE-2026-48913 and recommends current 2.4.x users move to that version. The latest source release is available from the Apache HTTP Server download page.
Verify the installed version after patching. Do not rely on package names alone. Distribution packages may backport security fixes while keeping an older upstream version string. Check your vendor advisory if you run Debian, Ubuntu, Red Hat, Rocky Linux, AlmaLinux, Amazon Linux, SUSE, a container base image, or a managed appliance.
If immediate patching is blocked, reduce exposure. Temporarily disable HTTP/2 on affected servers by removing h2 and h2c from Apache Protocols directives or by disabling the http2_module, then reload Apache. This is a risk-reduction step, not a replacement for patching.
Review file descriptor limits. Check service manager limits, Apache MPM settings, reverse proxy behavior, logging configuration, and connection handling. Watch for Too many open files errors, failed opens, abnormal child exits, and HTTP/2 stream resets. Resource exhaustion can become the trigger condition for this flaw.
Prioritize internet-facing systems first. Patch load balancers, reverse proxies, API gateways, shared hosting tiers, CDN origin servers, and any server that accepts untrusted HTTP/2 traffic. Then patch internal Apache tiers. Internal exposure still matters when services are reachable from compromised workloads or user-controlled clients.
Detection And Validation
Inventory Apache versions:
httpd -v
apache2 -v
Check whether mod_http2 is loaded:
httpd -M | grep http2
apache2ctl -M | grep http2
Check whether HTTP/2 is enabled in configuration:
grep -R "Protocols" /etc/httpd /etc/apache2 2>/dev/null
Look for h2 and h2c. The h2 token enables HTTP/2 over TLS. The h2c token enables cleartext HTTP/2. Systems without mod_http2 loaded and without HTTP/2 enabled have lower exposure to this specific flaw, but still need the broader 2.4.68 security review.
Container users must rebuild images. Restarting a container based on an old image does not apply the fix. Update the base image, rebuild application images, redeploy, and verify the running binary inside the container.
Timeline
May 22, 2026: CVE-2026-48913 was reported to the Apache security team, according to Apache’s advisory.
June 3, 2026: Apache fixed the issue in the 2.4.x branch with revision r1934882.
June 8, 2026: Apache HTTP Server 2.4.68 was released with the fix.
June 8, 2026: NVD received the CVE from the Apache Software Foundation.
June 10, 2026: NVD published initial analysis and listed affected Apache httpd versions from 2.4.55 up to, but not including, 2.4.68.
The vulnerability was also announced on the oss-security mailing list.
Related Patch Context
Apache HTTP Server 2.4.68 fixed multiple vulnerabilities, not only CVE-2026-48913. The same release also fixed CVE-2026-49975, a separate mod_http2 denial-of-service issue affecting Apache HTTP Server 2.4.17 through 2.4.67. Operators should review the full Apache 2.4 vulnerability list before deciding that one configuration is unaffected.
Do not patch only one host. Apache often sits in tiers: edge proxy, application proxy, admin console, artifact repository, monitoring endpoint, and legacy virtual host. A forgotten instance can keep the exposure alive.
Apply the update. Verify the module state. Monitor for file descriptor exhaustion. Treat repeated handle exhaustion as an incident precursor, not normal noise.
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