High [CVE-2026-78002] Rsyslog: rsyslog: denial of service via heap buffer overflow in rainerscript replace function
This high-severity Red Hat Linux advisory covers CVE-2026-78002 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7.
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Summary
A flaw was found in rsyslog. An unauthenticated remote attacker can trigger a heap buffer overflow in the RainerScript `replace()` function by sending specially crafted syslog messages.
This vulnerability arises from an incorrect buffer size calculation during string replacement, causing memory corruption. Successful exploitation can lead to a denial of service (DoS) for the affected system.
Red Hat Enterprise Linux systems configured to receive remote syslog messages are susceptible to this issue, potentially impacting logging availability. Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
Weakness: CWE-131. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9.
Red Hat does not currently list a fixing RHSA for this CVE.
Affected products named by the advisory: Red Hat package: rsyslog-crypto; Red Hat package: rsyslog-doc; Red Hat package: rsyslog-elasticsearch; Red Hat package: rsyslog-gnutls; and 26 more.
Affected products named by the advisory: Red Hat package: rsyslog-gssapi; Red Hat package: rsyslog-kafka; Red Hat package: rsyslog-mmaudit; Red Hat package: rsyslog-mmfields; and 22 more.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
Mitigation checklist
- To mitigate this vulnerability, restrict network access to the rsyslog service to only trusted hosts. This can be achieved by configuring firewall rules to limit incoming connections to UDP and TCP port 514. Alternatively, if remote syslog reception is not required, disable the `imudp` and `imtcp` modules in the `/etc/rsyslog.conf` configuration file. After modifying the rsyslog configuration or firewall rules, the rsyslog service or firewall service must be restarted for the changes to take effect.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
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