CVE-2026-19654
Description
A unauthenticated remote peer may lead rsyslogd to crash due to a flaw in the optional imptcp module. A crafted input sequence during oversize-frame recovery can cause an invalid internal message length and terminate rsyslogd. No confidentiality or integrity impact, privilege escalation, or code execution has been identified. imtcp and the default imptcp framing modes are not affected.
Statement
This vulnerability in rsyslog allows an unauthenticated peer to crash the rsyslogd deamon, resulting a a Denial-of-Service, by sending a crafted input sequence. This happens because the malicious input ends creating an invalid internal message length, which crashes the rsyslogd receiving the input. This vulnerability is only exploitable when the following conditions are met:
- imptcp module is explicitly loaded
- There's an imptcp listener using the non-default framing.delimiter.regex mode
- The attacker is able to establish a TCP connection to the target listener
Although this vulnerability has been rated as having an Important severity in upstream, the Red Hat Product Security team has rated it as having a MODERATE severity in supported Red Hat Products. This happens because the conditions described above are not met in default configurations of the rsyslog package as shipped with Red Hat Enterprise Linux Versions.
Mitigation
To mitigate this issue, users that are relying on the imptcp module can implement one of the following options:
1) Remove the framing.delimiter.regex from the affected
2) Disabled the affected `imptcp` listener or unload `imptcp` if it's not required
3) Restrict the network access to the listener to trusted senders only
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 | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
An attacker could get secret values such as cryptographic keys, PII, memory addresses, or other information that could be used in additional attacks.
Confidentiality
Technical Impact: Bypass Protection Mechanism
Out-of-bounds memory could contain memory addresses or other information that can be used to bypass ASLR and other protection mechanisms in order to improve the reliability of exploiting a separate weakness for code execution.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An attacker could cause a segmentation fault or crash by causing memory to be read outside of the bounds of the buffer. This is especially likely when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string.
Other
Technical Impact: Varies by Context
The read operation could produce other undefined or unexpected results.
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