Quick answers
- Is CVE-2026-55556 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-55556 being exploited in the wild.
- How severe is CVE-2026-55556?
- Informational severity, published 18 September 2026.
- Which products and versions are affected?
- Rsyslog 8.2110.0 to 8.2603.0.
- Is there a fix for CVE-2026-55556?
- A patch was published on 2026-09-18: Fixed in version 8.2604.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-55556 attacked?
- It is attacked over the network, in a hosted service.
- Am I affected by CVE-2026-55556?
- Check whether you run Rsyslog at an affected version. 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 imhttp module's parse_auth_header function allocates a zero-byte heap buffer when an HTTP Basic Authorization credential exceeds its fixed-size work buffer, then passes the invalid pointer to apr_base64_decode for decoding. This allows heap memory corruption before credential validation. The vulnerability is reachable by unauthenticated remote attackers over the network if imhttp with Basic Authentication is configured; current impact is denial of service via process crash.
Affected products
- rsyslog rsyslog 8.2110.0 to 8.2603.0
Timeline
- 2026-09-18: disclosed
- 2026-09-18: patched: Fixed in version 8.2604.0