# CVE-2026-78002: rsyslog heap buffer overflow in RainerScript replace function

Source: https://junglewise.ai/threats/cve-2026-78002-rsyslog-heap-buffer-overflow-in-rainerscript-replace-function  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-27. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-78002 · Severity: high · CVSS 7.5 · Published 2026-08-27

rsyslog is a critical system logging service used across enterprise infrastructure to collect, filter, and forward log messages. An unauthenticated attacker can trigger a heap buffer overflow by sending specially crafted syslog messages, causing the rsyslog daemon to crash and resulting in loss of logging functionality. This denial-of-service attack requires no authentication and can be exploited over the network, potentially blinding an organization to security events and operational issues.

Technologies: [Rsyslog](https://junglewise.ai/threats/technologies/rsyslog). Vendors: [Rsyslog](https://junglewise.ai/threats/vendors/rsyslog).

## Quick answers

**Is CVE-2026-78002 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-78002 being exploited in the wild.

**How severe is CVE-2026-78002?** High severity, with a CVSS score of 7.5, published 27 August 2026.

**Which products and versions are affected?** rsyslog rsyslog.

**Is there a fix for CVE-2026-78002?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-78002 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-78002?** Check whether you run Rsyslog. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a heap buffer overflow in the RainerScript `replace()` function, triggered by incorrect buffer size calculation during string replacement operations. An unauthenticated remote attacker can exploit this by sending specially crafted syslog messages over the network to a system running vulnerable rsyslog. The flaw leads to memory corruption that crashes the rsyslog daemon, resulting in denial of service. The attack vector is network-based with no authentication requirement, though no active exploitation in the wild has been reported. Patches addressing the buffer size calculation are expected from the rsyslog project.

## Affected products

- rsyslog rsyslog

## Timeline

- 2026-08-27: disclosed

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://catalog.redhat.com/software/containers/](https://catalog.redhat.com/software/containers/)

## Related threats

- [rsyslog omfile dynaFile path traversal](https://junglewise.ai/threats/cve-2026-92709-rsyslog-is-a-rocket-fast-system-for-log-processing-from-versions)
- [Rsyslog imhttp heap buffer overflow in Basic Authentication parsing](https://junglewise.ai/threats/cve-2026-55556-rsyslog-is-a-rocket-fast-system-for-log-processing-from-8-2110-0)
- [rsyslog denial of service in imptcp module](https://junglewise.ai/threats/cve-2026-19654-rsyslog-denial-of-service-in-imptcp-module)