SB2026080502 - Red Hat Enterprise Linux 9 update for mod_http2
Published: August 5, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 4 vulnerabilities.
1) Resource management error (CVE-ID: CVE-2025-53020)
CWE-ID: CWE-399 - Resource Management Errors
CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to improper management of internal resources within the server when handling HTTP/2 requests. A remote attacker can send multiple requests to the server and perform a denial of service (DoS) attack.
2) Resource exhaustion (CVE-ID: CVE-2026-49975)
CWE-ID: CWE-400 - Resource exhaustion
CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to uncontrolled resource consumption in the HTTP/2 request handling and HPACK header processing when handling crafted HTTP/2 requests that use repeated indexed header references and a stalled flow-control window. A remote attacker can send specially crafted HTTP/2 requests to cause a denial of service.
The issue is reachable in the default HTTP/2 configuration.
3) Use-after-free (CVE-ID: CVE-2026-48913)
CWE-ID: CWE-416 - Use After Free
CVSSv4: 9.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to use-after-free in mod_http2 when file handles are already exhausted. A remote attacker can trigger request processing under file descriptor exhaustion conditions to execute arbitrary code.
Exploitation requires the server to have exhausted file handles.
4) Out-of-bounds read (CVE-ID: CVE-2026-43951)
CWE-ID: CWE-125 - Out-of-bounds read
CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to out-of-bounds read in merge_response_headers when processing responses with mod_headers, mod_mime, and multiple response languages. A remote attacker can trigger processing of affected responses to cause a denial of service.
The issue occurs when mod_headers and mod_mime are used with multiple response languages.
Remediation
Install update from vendor's website.