CVE-2026-78002

Rsyslog: rsyslog: denial of service via heap buffer overflow in rainerscript replace() function

publishedCWE-131

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.

Technical severity7.5 highCVSS 3.1 · CNA: redhat

Published2026-08-27Source updated 2026-11-04

Collected2026-11-052 attributed sources

Fixes and workarounds

Workaround

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.

Source: CNA: redhat

Affected products and versions

Affected products, source version ranges and reporting authorities
Product	Versions	Authority
Red Hat Enterprise Linux 10 Red Hat `rsyslog` https://access.redhat.com/downloads/content/package-browser/	≥ 0:8.2510.0-5.el10_2.2; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 10.0 Extended Update Support Red Hat `rsyslog` https://access.redhat.com/downloads/content/package-browser/	≥ 0:8.2412.0-1.el10_0.2; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 8 Red Hat `rsyslog` https://access.redhat.com/downloads/content/package-browser/	≥ 0:8.2102.0-15.el8_10.3; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support Red Hat `rsyslog` https://access.redhat.com/downloads/content/package-browser/	≥ 0:8.2102.0-7.el8_6.2; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On Red Hat `rsyslog` https://access.redhat.com/downloads/content/package-browser/	≥ 0:8.2102.0-7.el8_6.2; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 8.8 Telecommunications Update Service Red Hat `rsyslog` https://access.redhat.com/downloads/content/package-browser/	≥ 0:8.2102.0-13.el8_8.1; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions Red Hat `rsyslog` https://access.redhat.com/downloads/content/package-browser/	≥ 0:8.2102.0-13.el8_8.1; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 9 Red Hat `rsyslog` https://access.redhat.com/downloads/content/package-browser/	≥ 0:8.2510.0-2.el9_8.2; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions Red Hat `rsyslog` https://access.redhat.com/downloads/content/package-browser/	≥ 0:8.2102.0-113.el9_2.3; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions Red Hat `rsyslog` https://access.redhat.com/downloads/content/package-browser/	≥ 0:8.2310.0-4.el9_4.2; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 9.6 Extended Update Support Red Hat `rsyslog` https://access.redhat.com/downloads/content/package-browser/	≥ 0:8.2412.0-1.el9_6.2; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Update Infrastructure 5 Red Hat `rhui5/haproxy-rhel9` https://catalog.redhat.com/software/containers/	≥ 1790241900; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 6 Red Hat `rsyslog` https://access.redhat.com/downloads/content/package-browser/	Range not reported Other versions: unaffected	CNA: redhat
Red Hat Enterprise Linux 6 Red Hat `rsyslog7` https://access.redhat.com/downloads/content/package-browser/	Range not reported Other versions: unaffected	CNA: redhat
Red Hat Enterprise Linux 7 Red Hat `rsyslog` https://access.redhat.com/downloads/content/package-browser/	Range not reported Other versions: affected	CNA: redhat

Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.

CVSS assessments

CVSS scores, vectors and reporting authorities
Version / score	Vector	Authority
3.1 / 7.5 high	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`	CNA: redhat

Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

References

https://access.redhat.com/errata/RHSA-2026:69540CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:69541CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:71603CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:80817CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:81321CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:84576CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:86124CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:87408CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:90349CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:91582CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/security/cve/CVE-2026-78002CNA: redhat · vdb-entry, x_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2521135CNA: redhat · issue-tracking, x_refsource_REDHAT
https://github.com/rsyslog/rsyslog/security/advisories/GHSA-g72f-gc6v-f2w3CNA: redhat
http://www.openwall.com/lists/oss-security/2026/08/29/1ADP: CVE

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