CVE-2026-92392
Description
A flaw was found in curl. When curl uploads data over an HTTP/2 connection, it mishandles server stream reset frames, which can lead to the reuse of previously released memory. Under specific memory and timing conditions, a malicious server can exploit this flaw to execute arbitrary code on the client system or cause the application to crash, resulting in a Denial of Service (DoS).
Statement
Red Hat has rated this flaw as having an Important severity because a malicious HTTP/2 server can remotely trigger memory corruption during data uploads, potentially leading to client application crashes or arbitrary code execution. While remote code execution has been demonstrated, exploitation requires strict prerequisites such as exact heap layout predictability and precise server-controlled timing, which limits broad automated exploitability. Earlier versions of Red Hat Enterprise Linux, including RHEL 8 and 9, are not vulnerable as they ship curl builds preceding the introduction of the flawed logic.
Mitigation
Disable HTTP/2 in curl. For the curl CLI, use the `--http1.1` flag. For applications using libcurl, set `CURLOPT_HTTP_VERSION` to `CURL_HTTP_VERSION_1_1`. This vulnerability is only exploitable over HTTP/2 connections; HTTP/1.1 connections are not affected. Note that applications which depend on HTTP/2-specific features, such as gRPC, will not function with this workaround.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.1 | N/A | 8.1 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory
The use of previously freed memory may corrupt valid data, if the memory area in question has been allocated and used properly elsewhere.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If chunk consolidation occurs after the use of previously freed data, the process may crash when invalid data is used as chunk information.
Confidentiality
Technical Impact: Read Memory
Read operations on freed memory can sometimes leak sensitive information instead of causing a crash
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If malicious data is entered before chunk consolidation can take place, it may be possible to take advantage of a write-what-where primitive to execute arbitrary code. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.
Acknowledgements
Red Hat would like to thank Luna with Claude (Anthropic) for reporting this issue.
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