# CVE-2026-78002: Rsyslog: rsyslog: denial of service via heap buffer overflow in rainerscript replace() function

Status: published. Published: 2026-08-27. Updated: 2026-11-04.

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.

## Remediation

- 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

- Red Hat / Red Hat Enterprise Linux 10 (rsyslog): ≥ 0:8.2510.0-5.el10_2.2; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 10.0 Extended Update Support (rsyslog): ≥ 0:8.2412.0-1.el10_0.2; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (rsyslog): ≥ 0:8.2102.0-15.el8_10.3; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support (rsyslog): ≥ 0:8.2102.0-7.el8_6.2; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On (rsyslog): ≥ 0:8.2102.0-7.el8_6.2; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8.8 Telecommunications Update Service (rsyslog): ≥ 0:8.2102.0-13.el8_8.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions (rsyslog): ≥ 0:8.2102.0-13.el8_8.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (rsyslog): ≥ 0:8.2510.0-2.el9_8.2; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions (rsyslog): ≥ 0:8.2102.0-113.el9_2.3; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions (rsyslog): ≥ 0:8.2310.0-4.el9_4.2; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9.6 Extended Update Support (rsyslog): ≥ 0:8.2412.0-1.el9_6.2; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Update Infrastructure 5 (rhui5/haproxy-rhel9): ≥ 1790241900; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (rsyslog): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (rsyslog7): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (rsyslog): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: redhat

- CISA KEV: No listing in collected sources

- EPSS: 1.06% as of 2026-11-04; percentile 64.76%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-131

## Exploit evidence

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

## References

- https://access.redhat.com/errata/RHSA-2026:69540 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:69541 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:71603 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:80817 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:81321 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:84576 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:86124 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:87408 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:90349 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:91582 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-78002 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2521135 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://github.com/rsyslog/rsyslog/security/advisories/GHSA-g72f-gc6v-f2w3 (CNA: redhat)

- http://www.openwall.com/lists/oss-security/2026/08/29/1 (ADP: CVE)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-78002; retrieved 2026-11-05; source updated 2026-11-04

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-78002; retrieved 2026-11-05; source updated Not reported

Revision: 143dc82dc5fd695bc6bf9e762094cb9686c1097beb237c6cbe33c47ba49bb5c6

Canonical: https://y2.dev/cve/CVE-2026-78002

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