CVE-2026-31427
Description
A flaw was found in the Linux kernel's netfilter subsystem, specifically within the nf_conntrack_sip module. This vulnerability occurs in the process_sdp function when the rtp_addr variable is used without proper initialization if the Session Description Protocol (SDP) body lacks recognized media types or active media sections. A remote attacker could potentially exploit this by sending specially crafted SDP messages, leading to the rewriting of session-level owner and connection addresses with uninitialized or stale stack values. This could result in information disclosure or unexpected network behavior, potentially causing a denial of service.
Statement
The bug is confined to SIP sessions handled by the connection-tracking helper and NAT SDP hooks. It requires SIP traffic traversing a host with nf_conntrack_sip (and relevant NAT) loaded. Integrity of signaling is affected; remote attackers who can pass SDP through the helper can influence rewritten addresses. Scope should be reviewed against whether IPv4/IPv6 SIP transit applies (network vs. strictly local control plane).
Mitigation
To mitigate this issue, prevent the `nf_conntrack_sip` module from being loaded when SIP helper/NAT is not required. See https://access.redhat.com/solutions/41278 for instructions.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.8 | 5.5 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | Low | None | N/A |
| Integrity Impact | Low | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
If the uninitialized pointer is used in a read operation, an attacker might be able to read sensitive portions of memory.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If the uninitialized pointer references a memory location that is not accessible to the product, or points to a location that is "malformed" (such as NULL) or larger than expected by a read or write operation, then a crash may occur.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If the uninitialized pointer is used in a function call, or points to unexpected data in a write operation, then code execution may be possible.
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