Vulnerability in Smallnest Rpcx
CVE-2026-59803
rpcx through 1.9.3, fixed in commit 047aec1, contains a denial-of-service vulnerability in protocol.Message.Decode (protocol/message.go). When a message has the compression flag set, the payload is gzip-decompressed via util.Unzip with no limit on the decompressed output size. The only built-in size guard, protocol.MaxMessageLength, is checked against the compressed on-the-wire frame length, not the decompressed size, so it provides no protection. Because decoding (and decompression) occurs in readRequest before authentication, a single unauthenticated connection can send a small (under 2 MB) gzip-compressed message that expands to gigabytes of heap allocation, leading to out-of-memory conditions and service unavailability.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.007 (53.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 53rd percentile — 53.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000
Affected products
- Smallnest Rpcx — versions 0, 047aec18efa7d037105e2b72c36dd2ae05e1acc6
Weakness classification (CWE)
References
- github.com/smallnest/rpcx/issues/942 (technical-description, exploit)
- github.com/smallnest/rpcx/pull/943 (issue-tracking)
- github.com/smallnest/rpcx/commit/047aec18efa7d037105e2b72c36dd2ae05e1acc6 (patch)
- www.vulncheck.com/advisories/rpcx-denial-of-service-via-gzip-decompression-bomb… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-59803?
- CVE-2026-59803 is a high-severity vulnerability in Smallnest Rpcx, classified under Improper Handling of Highly Compressed Data (Data Amplification). CVSS score: 7.5/10. Published 2026-07-08.
- How severe is CVE-2026-59803?
- High severity. CVSS v3 base score is 7.5 out of 10.