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TL;DR
Apache released HTTP Server 2.4.71 on November 11 to fix CVE-2026-119618, a critical mod_http2 flaw that Apache says can lead to remote code execution. The issue affects versions 2.4.55 through 2.4.70 when HTTP/2 is enabled; exploitation in the wild has not been confirmed in the cited sources, but Red Hat says public research has demonstrated a reliable exploit.
The Apache HTTP Server project released version 2.4.71 on November 11 to fix CVE-2026-119618, a critical flaw in its mod_http2 module that Apache says can lead to remote code execution. The issue affects Apache HTTP Server versions 2.4.55 through 2.4.70 when HTTP/2 is enabled, so system owners should check their installed packages and configuration.
Apache describes the issue as a concurrent execution and improper synchronization vulnerability in the mod_http2 function assign_headers. The affected code handles HTTP/2 requests, which can be processed in parallel over a single connection. Red Hat says a thread-safety flaw can allow one thread to modify memory used by another, corrupting the server’s internal memory. Apache characterizes the result as heap corruption that can lead to remote code execution.
Red Hat says a remote attacker able to reach an affected web server could exploit the flaw to execute arbitrary commands without authentication. Red Hat assigns it a CVSS 3.1 score of 9.8 out of 10; the National Vulnerability Database had not published its own score as of the source report’s November 12 check. Apache’s advisory lists the affected HTTP Server releases as 2.4.55 through 2.4.70, and separately identifies standalone mod_h2 versions 2.0.8 through 2.0.42 from GitHub.
The immediate action depends on how Apache was installed. The upstream fix is Apache HTTP Server 2.4.71, but administrators using distribution packages should follow their vendor’s fixed package and advisory. Red Hat shipped fixes on November 11, including advisories for RHEL 9 and 10. Debian’s stable bookworm and trixie releases were still listed as vulnerable in the report; version 2.4.71-1 had reached Debian’s unstable sid branch. The source reported no published Ubuntu or SUSE advisory at the time it checked.
Apache HTTP/2 flaw What system owners should do
Apache 2.4.71 fixes CVE-2026-119618, a critical mod_http2 flaw that can lead to remote code execution. Exposure depends on both the server version and whether HTTP/2 is enabled.
Check both conditions
The flaw affects versions in the listed range when HTTP/2 is enabled.
- Check whether Apache is 2.4.55 through 2.4.70.
- Distribution packages may backport fixes without changing the upstream version string.
- Verify whether h2 or h2c is enabled through the Protocols directive.
- Red Hat says servers serving only HTTP/1.1 are not affected.
How the flaw can affect servers
Concurrent HTTP/2 request handling can expose shared memory to improper synchronization.
A thread can modify memory used by another thread.
Apache says the corruption can lead to remote code execution.
Red Hat says a reachable affected server could allow unauthenticated command execution.
Exposure signals have limits
Available reports describe different parts of the risk and do not establish widespread exploitation.
Customer environment data
Wiz reported 64% of cloud environments in its customer data had vulnerable resources and 51% had publicly exposed instances. The figures do not account for configuration.
Reliable exploit reported
Red Hat says public research demonstrated a reliable exploit against a default-configured server with mod_http2 enabled.
No confirmed in-the-wild use
Wiz reported no known exploitation in the wild; the cited material does not confirm active attacks.
Patch status depends on the vendor
Use product-specific security guidance to determine whether your installed package is fixed.
| Source or release | Reported status |
|---|---|
| Apache HTTP Server | 2.4.71 fixes the flaw |
| Red Hat | Fixes shipped November 11 for RHEL 9 and 10 |
| Debian stable | Bookworm and trixie listed as vulnerable in the report |
| Debian unstable | 2.4.71-1 had reached sid |
| Ubuntu and SUSE | No advisory published at the time checked |
Owner action checklist
Confirm exposure, then follow the fix path for the way Apache is installed.
- Inventory Apache packages and identify releases in the affected range.
- Check configuration for h2 or h2c; do not assume the default protocol setting.
- Apply Apache 2.4.71 or the vendor’s fixed package and advisory guidance.
- Monitor vendor notices where guidance was not yet published.
Why HTTP/2 Configuration Matters
The flaw’s reported severity makes the combination of network reachability and HTTP/2 exposure important for operators to assess. Red Hat says the issue affects servers with HTTP/2, using h2 or h2c, enabled through the Protocols directive. It says servers serving only HTTP/1.1 are not affected. Apache documentation cited in the report lists HTTP/1.1 as the default protocol setting, but administrators should inspect their actual configuration rather than assume the default is in use.
Wiz reported that 64% of cloud environments in its customer data had resources vulnerable to this CVE and that 51% had publicly exposed instances. Wiz cautioned that its figures do not account for configuration. They are measurements from the company’s customer environments, not a global count of vulnerable or exploitable servers. They nevertheless illustrate why identifying package versions alone may not establish whether a particular server is exposed.
There is also a gap between public reporting and exploit-risk claims. Wiz said it had seen no reports of exploitation in the wild and no available exploit when its November 11 post appeared. Red Hat, however, said public research had demonstrated a reliable exploit against a default-configured server with mod_http2 enabled. That statement does not establish that attackers are using the exploit, but it is a reason for affected operators to treat remediation as urgent rather than wait for evidence of attacks.
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Reports, Patch and Vendor Status
Apache credited Anthropic’s OSS Scanner and two researchers from Google Cloud Vulnerability Research with finding the flaw. According to the source report, Anthropic’s report reached Apache on October 26, and Google Cloud’s report followed on November 3. The CVE number was reserved on October 30. Apache released the fix on November 11, a 16-day span from the first report to the release.
Vendor assessments differ in scope and severity. Red Hat rates the flaw critical overall but important for RHEL 9 and 10, explaining that those systems’ mod_http2 packages use a separate allocator for each HTTP/2 stream, which it says makes exploitation more complex. RHEL 8 and earlier are listed as not affected; Red Hat JBoss Core Services and Red Hat Hardened Images were still listed as affected in the report. Administrators should consult the advisory for the precise status of their product and package.
The flaw is in Apache’s HTTP/2 module, not a general claim that every Apache server is vulnerable. Both version and protocol configuration matter: an affected release with HTTP/2 disabled is not described by Red Hat as exposed to this issue, while a vendor may backport a fix without changing the upstream version number. For distribution-managed systems, package status and vendor guidance are more useful than comparing version strings alone.
“A Concurrent Execution using Shared Resource with Improper Synchronization vulnerability in Apache HTTP Server’s mod_http2 in assign_headers() can lead to RCE.”
— Apache HTTP Server security advisory
Exploit Activity and Exposure Gaps
Confirmed exploitation in the wild was not established in the source material. Wiz reported no known in-the-wild exploitation as of its November 11 post, and the CVE was not on CISA’s Known Exploited Vulnerabilities catalog when checked on November 12. The cited report notes that the catalog version available at that time predated public disclosure, limiting what its absence can show.
Red Hat’s statement that public research demonstrated a reliable exploit raises concern, but the report does not name the researchers or say whether the work was publicly released. The advisories cited did not link to public exploit code. The number of affected servers also remains unknown: Wiz’s percentages describe its own customer data and do not account for configuration. Vendor status may change, particularly for distributions without an advisory in the November 12 check.
Patch Checks and Vendor Advisories
Administrators should identify Apache installations in the affected version range, verify whether h2 or h2c is enabled, and apply Apache 2.4.71 or the vendor’s fixed package. Where a vendor has not yet published guidance, owners should monitor its security advisories and avoid treating the upstream version number as the only indicator of package status. Red Hat’s report also lists some related products as affected, so operators should check product-specific notices.
The next confirmed developments will be updated vendor package information and any changes to public exploit or incident reporting. The source material does not give a deadline for remaining distributions to issue fixes, nor does it confirm active attacks. Until those details change, system owners should base their response on the affected version, HTTP/2 configuration and applicable vendor advisory.
Key Questions
Which Apache versions are affected?
Apache lists HTTP Server versions 2.4.55 through 2.4.70 as affected. The source report also lists standalone mod_h2 versions 2.0.8 through 2.0.42. The upstream fixed release is 2.4.71.
Does the flaw affect servers that use only HTTP/1.1?
Red Hat says servers serving only HTTP/1.1 are not affected. It identifies HTTP/2 configurations using h2 or h2c as affected. Check the server’s active Protocols configuration rather than relying on assumptions about defaults.
Is CVE-2026-119618 being exploited?
The cited material does not confirm attacks in the wild. Wiz reported no known in-the-wild exploitation as of November 11, while Red Hat said public research had demonstrated a reliable exploit. Those statements concern different evidence; confirmed attacker use remains unclear.
What should system owners install?
Install Apache HTTP Server 2.4.71 or the fixed package provided by the relevant Linux distribution or product vendor. Distribution packages may include backported fixes, so consult the vendor advisory for the exact package status.
Source: ThorstenMeyerAI.com
