CVE-2022-24903: Rsyslog is a rocket-fast system for log processing. Modules for TCP syslog reception have a potential heap buffer overflow when octet-counted framing ...

Description

Rsyslog is a rocket-fast system for log processing. Modules for TCP syslog reception have a potential heap buffer overflow when octet-counted framing is used. This can result in a segfault or some other malfunction. As of our understanding, this vulnerability can not be used for remote code execution. But there may still be a slight chance for experts to do that. The bug occurs when the octet count is read. While there is a check for the maximum number of octets, digits are written to a heap buffer even when the octet count is over the maximum, This can be used to overrun the memory buffer. However, once the sequence of digits stop, no additional characters can be added to the buffer. In our opinion, this makes remote exploits impossible or at least highly complex. Octet-counted framing is one of two potential framing modes. It is relatively uncommon, but enabled by default on receivers. Modules `imtcp`, `imptcp`, `imgssapi`, and `imhttp` are used for regular syslog message reception. It is best practice not to directly expose them to the public. When this practice is followed, the risk is considerably lower. Module `imdiag` is a diagnostics module primarily intended for testbench runs. We do not expect it to be present on any production installation. Octet-counted framing is not very common. Usually, it needs to be specifically enabled at senders. If users do not need it, they can turn it off for the most important modules. This will mitigate the vulnerability.

Metrics

CVSS 3.1

8.1/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

3.55%

87.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Rsyslog	Rsyslog	< 8.2204.1
Fedoraproject	Fedora	35
Debian	Debian Linux	9.0
Debian	Debian Linux	10.0
Debian	Debian Linux	11.0
Netapp	Active Iq Unified Manager	All versions

References

https://github.com/rsyslog/rsyslog/commit/f211042ecbb472f9d8beb4678a65d272b6f07705Patch, Third Party Advisory
https://github.com/rsyslog/rsyslog/security/advisories/GHSA-ggw7-xr6h-mmr8Third Party Advisory
https://lists.debian.org/debian-lts-announce/2022/05/msg00028.htmlMailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GMNNXLCU2UORRVSZO24HL4KMVPK5PHVW/
https://security.netapp.com/advisory/ntap-20221111-0002/Third Party Advisory
https://www.debian.org/security/2022/dsa-5150Third Party Advisory
https://github.com/rsyslog/rsyslog/commit/f211042ecbb472f9d8beb4678a65d272b6f07705Patch, Third Party Advisory
https://github.com/rsyslog/rsyslog/security/advisories/GHSA-ggw7-xr6h-mmr8Third Party Advisory
https://lists.debian.org/debian-lts-announce/2022/05/msg00028.htmlMailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GMNNXLCU2UORRVSZO24HL4KMVPK5PHVW/
https://security.netapp.com/advisory/ntap-20221111-0002/Third Party Advisory
https://www.debian.org/security/2022/dsa-5150Third Party Advisory

Timeline

Published: May 6, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2022-24903?

Rsyslog is a rocket-fast system for log processing. Modules for TCP syslog reception have a potential heap buffer overflow when octet-counted framing is used. This can result in a segfault or some other malfunction. As of our understanding, this vulnerability can not be used for remote code execution. But there may still be a slight chance for experts to do that. The bug occurs when the octet count is read. While there is a check for the maximum number of octets, digits are written to a heap buffer even when the octet count is over the maximum, This can be used to overrun the memory buffer. However, once the sequence of digits stop, no additional characters can be added to the buffer. In our opinion, this makes remote exploits impossible or at least highly complex. Octet-counted framing is one of two potential framing modes. It is relatively uncommon, but enabled by default on receivers. Modules `imtcp`, `imptcp`, `imgssapi`, and `imhttp` are used for regular syslog message reception. It is best practice not to directly expose them to the public. When this practice is followed, the risk is considerably lower. Module `imdiag` is a diagnostics module primarily intended for testbench runs. We do not expect it to be present on any production installation. Octet-counted framing is not very common. Usually, it needs to be specifically enabled at senders. If users do not need it, they can turn it off for the most important modules. This will mitigate the vulnerability.

How severe is CVE-2022-24903?

CVE-2022-24903 has a CVSS score of 8.1/10 (HIGH severity). The EPSS model estimates a 3.55% probability of exploitation in the next 30 days.

How do I fix CVE-2022-24903?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.